Patent Application
20240083846
The present invention is related to SMAC (Second Mitochondria-derived Activator of Caspase) mimetic compounds useful for treatment of proliferative disorder including cancer.
Evasion of apoptosis or ‘programmed cell-death’ is one of the hallmarks of human cancer. Therefore, restoration or induction of apoptosis in cancer cells is an attractive therapeutic strategy. There are multiple endogenous cellular counter acting proteins that regulate intricate balance between cell death and survival. One of the classical examples of such reciprocal regulation within cell is the interaction between SMAC and IAP. The SMAC is a pro-apoptotic protein, sensitizes cells to apoptosis in cancerous cells by antagonizing the activity of IAPs. Therefore, SMAC mimetics have been found as a novel and targeted therapeutic approach to treat cancer (Abraha et. al, World J Gastrointest Oncol. Aug. 15, 2016; 8(8): 583-591). Currently, multiple clinical trials are ongoing for different SMAC mimetics against various cancer types demonstrating its immense importance in cancer therapeutics (Fulda et. al., Clinical Cancer Research. Volume 21, Issue 22, 2015. 5030-5036).
The Inhibitors of Apoptosis Proteins (IAPs) are naturally occurring intra-cellular proteins that suppress caspase-dependent apoptosis. IAPs are the key negative regulators that inhibit the distinct caspases which are critical for initiation and execution of apoptotic pathways. There are eight members in the mammalian IAP family. Among these X-chromosome-linked IAP (XIAP) is perhaps the best characterized member of IAPs family that is known to play a direct role in the regulation of apoptosis. XIAP bind to caspase-3 and caspase-7 via its BIR2 domain and the preceding linker region, respectively. In addition, XIAP also binds to caspase-9 via its BIR3 domain, thereby blocking the dimerization and subsequent activation of caspase-9. Given that fact caspase-3 and -7 play a major role in the implementation of apoptosis in both the extrinsic and intrinsic pathways, and caspase-9 is a critical initiator caspase in the intrinsic pathway, XIAP is the most preferable target to revive the apoptosis. SMAC is the naturally available antagonist of IAP proteins. SMAC is released from the mitochondria into the cytosol upon apoptotic signalling and binds to the BIR3 domain of XIAP via conserved IAP-binding motif (IBM) which contains four amino acid residues (AVPI) that is exposed at the amino-terminus of the mature processed SMAC protein and prevent the interaction of XIAP with caspases (Cong et. al., J. Med. Chem. 2019, 62, 5750-5772).
In addition, Smac also binds to the BIR3 domain of cIAP1 and cIAP2 and as a result enhances their E3 ligase activity which promotes the auto-ubiquitination and proteasomal degradation of cIAP1 and cIAP2. Several small molecule mimetics of AVPI, termed IAP inhibitors are being advanced in clinical trials for the treatment of cancer. The LCL-161 and AT-406 are structurally monovalant whereas Birinapant/TL32711 is a bivalent are among the prominent ones under development.
The major approach used for the designing the SMACs are focussed on the synthesis of conformationally constrained compounds where Xxx-Pro bond is preferably in trans geometry. Yet another consideration was undertaken is the balance of lipophilicity at the C-terminal end or of the linkers for the bivalent molecules. Several efforts are made in the past for the evolution of Smac AVPI tetrapeptide to develop bioavailable Smac mimetics by systematically examination of the role and tolerance to substitution of each amino acids of AVPI (1) peptide.
A library of tetrapeptides using the N-terminal of Smac are prepared with a novel strategy to control trans geometry around the proline residue as a starting point. They replaced the position of each one of the four amino acids with all the natural amino acids. It is found that alanine residue at position 1 of the tetrapeptide is very crucial for activity and binding is greatly diminished if alanine is replaced with any natural amino acids.
Therefore, there is a need in the art for new compounds, which are capable of restoring or inducing apoptosis in cancer cells for treatment of cancer.
The main objective of the present invention is to develop peptide SMAC mimetics useful as monotherapy as well as in combination with available anti-cancer drugs as safe and effective therapy against various types of cancer.
Another objective of the invention is to develop a process for the synthesis of SMAC mimetics.
Yet another objective of the present invention is to develop formulations of SMAC mimetics suitable for human application.
Still another objective of the present invention is treatment of cancer using SMAC mimetics.
Another objective of the present invention is to provide targeted therapy against treatment resistance cancer by using SMAC mimetics.
Yet another objective of the present invention is to provide SMAC mimetic or IAP antagonist or IAP inhibitor having the capability to potently bind both BIR-2 and BIR-3 domains of XIAP/IAP and having significant bioavailability with robust in-vitro and in-vivo efficacy against therapy resistant refractory cancers.
An aspect of the present invention provides a SMAC mimetic compound of Formula-I,
Another aspect of the present invention provides the SMAC mimetic compound selected from the group consisting of
Yet another aspect of the present invention provides a process for preparation of SMAC mimetics compound of Formula-I,
Another aspect of the present invention provides a process comprising removal of Boc-group 2-benzyl 1-(tert-butyl) (2S ,5S)-5-(5-methylfuran-2-yl)pyrrolidine-1,2-dicarboxylate followed by the coupling of the resulting amine with Boc-Val-OH to obtain a compound II of which the Boc-group is deprotected followed by its coupling with Boc-Ala-OH to provide a compound III of which the ester is saponified to carboxylic acid followed by its coupling with either H-Ile-OBn or benzhydryl amine followed by its acidolysis to furnish a compound 2 and 3, respectively.
Another aspect of the present invention provides a process comprising removal of Boc-group from a compound II followed by its coupling with Boc-N-Me-Ala-OH to provide 25 a compound V of which the ester is saponified to carboxylic acid followed by its coupling with either H-Ile-OBn or benzhydryl amine or H-Ile-benzhydryl amide followed by its acidolysis to yield compounds 4, 5, and 6, respectively.
An aspect of the present invention provides a process comprising removal of Boc-group from the intermediate I followed by coupling of the resulting amine with Boc-Chg-OH to obtain a compound VII of which the Boc-group is deprotected followed by coupling with Boc-N-Me-Ala-OH to obtain a compound VIII of which the ester is converted to carboxylic acid followed by its coupling with either H-Ile-OBn or benzhydryl amine followed by its acidolysis to obtain compounds 7, 8 and 9, respectively,
Another aspect of the present invention provides a process for preparation of SMAC mimetic compound (2S ,5R)-N-((2S ,3S)-1 -(benzhydrylamino)-3-methyl-1 -oxopentan-2-yl)- 1 -((S)-3 -methyl-2-((S)-2-(methylamino)prop anamido)butanoyl)-5-phenylpyrrolidine-2-carboxamide (10), comprising the steps of;
Another aspect of the present invention provides a compound of Formula-I, which inhibits the binding of SMAC protein to Inhibitor of Apoptosis Proteins(IAPs) and is useful in treatment of proliferative diseases including cancer.
Yet another aspect of the present invention provides a pharmaceutical composition comprising SMAC mimetic compound of Formula-I,
Still another aspect of the present invention provides a pharmaceutical composition comprising SMAC mimetic compound of Formula-I,
In an aspect of the present invention, the SMAC mimetic compound of Formula I have potent anti-proliferative activity against various mammalian cancer cell lines selected from the group consisting of colon, breast, kidney, prostate, brain, ovary, pancreas, melanoma, liver, leukemia and lymphoma.
In another aspect of the present invention, the SMAC mimetic compound is useful in treatment of therapy resistant, refractory, and metastatic cancers in mammals.
In yet another aspect of the present invention, the SMAC mimetic compound is useful in combination therapies with other anti-proliferative agents selected from the group consisting of TRAIL agonists/MAbs, aromatase inhibitors, epigenetic modulators, kinase inhibitors, alkylating agents, microtubule disrupters, topoisomerase inhibitors, antiangiogenic compounds, Hsp90 inhibitors, mTOR inhibitors, estrogen and androgen antagonists, MMP inhibitors and biological response modifiers.
Another aspect of the present invention provides a method for treating cancer using SMAC mimetic compound of Formula I.
Yet another aspect of the present invention provides a method for treating cancer using SMAC mimetic compounds of Formula-I having the capability to bind to both BIR-2 and BIR-3 domains of XIAP/IAP and having significant bioavailability with robust in-vitro and in-vivo efficacy against therapy resistant refractory cancers.
SMAC: second mitochondrial-derived activator of caspases
TRAIL: tumor necrosis factor-related apoptosis inducing ligand
The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated.
For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are delineated here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skilled in the art. The terms used herein have the meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.
The articles “a”, “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.
The terms “comprise” and “comprising” are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as “consists of only”.
Throughout this specification, unless the context requires otherwise the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.
The present invention relates to SMAC mimetics of Formula-I exhibiting strong anticancer potential in vitro as well as in vivo via apoptotic pathways.
The present invention is directed towards a SMAC mimetic compound of Formula-I,
In an embodiment of the present invention, there is provided a SMAC mimetic compound of Formula I selected from the group consisting of
Another embodiment of the present invention provides a process for preparation of SMAC mimetics compound of Formula-I,
In an embodiment of the present invention, there is provided a process for preparation of SMAC mimetics compound of Formula-I, wherein the peptide coupling reagent is selected from the group consisting of HOBt, EDCI and HBTU.
In another embodiment of the present invention, there is provided a process for preparation of SMAC mimetics compound of Formula-I, wherein the weak base is diethylisopropylamine.
In yet another embodiment of the present invention, there is provided a process for preparation of SMAC mimetics compound of Formula-I, wherein the Pd-catalyst is selected from Pd/C, or Pd(OH)2/C.
In still another embodiment of the present invention, there is provided a process for preparation of SMAC mimetics compound of Formula-I, wherein the solvent is selected from DCM, or DMF for peptide coupling.
In an embodiment of the present invention, there is provided a process for preparation of SMAC mimetics compound of Formula-I, wherein the solvent is selected from MeOH, or EtOAc for catalytic hydrogenation.
In another embodiment of the present invention, there is provided a process of preparation of SMAC mimetic compound 10, comprising the steps of;
In yet another embodiment of the present invention, there is provided a process of preparation of SMAC mimetic compound 10, wherein the peptide coupling reagent is selected from the group consisting of HOBt, EDCI and HBTU.
In still another embodiment of the present invention, there is provided a process of preparation of SMAC mimetic compound 10, wherein the solvent is selected from DCM, or DMF.
In another embodiment of the present invention, there is provided a process of preparation of SMAC mimetic compound 10 wherein the weak base is diethylisopropylamine.
In yet another embodiment of the present invention, there is provided a process of preparation of SMAC mimetic compound 10, wherein the reagent for acidolysis is TFA.
In another embodiment of the present invention, there is provided a SMAC mimetic compound of Formula I, wherein the compound inhibits binding of Smac protein to Inhibitor of Apoptosis Proteins(IAPs) and is useful in treatment of proliferative diseases including cancer.
Yet another embodiment of the present invention provides a pharmaceutical composition comprising SMAC mimetic compound of Formula-I,
Still another embodiment of the present invention provides a pharmaceutical composition comprising SMAC mimetic compound of Formula-I,
In another embodiment of the present invention, there is provided a SMAC mimetic compound of Formula I having potent anti-proliferative activity against mammalian cancer cell lines selected from the group consisting of colon, breast, kidney, prostate, brain, ovary, pancreas, melanoma, liver, leukemia and lymphoma.
In yet another embodiment of the present invention, there is provided a SMAC mimetic compound of Formula I, wherein the compound is useful in treatment of therapy resistant, refractory, and metastatic cancers in mammals.
In still another embodiment of the present invention, there is provided a SMAC mimetic compound of Formula I, wherein the compound is useful in combination therapies with other anti-proliferative agents selected from the group consisting of TRAIL agonists/MAbs, aromatase inhibitors, epigenetic modulators, kinase inhibitors, alkylating agents, microtubule disrupters, topoisomerase inhibitors, antiangiogenic compounds, Hsp90 inhibitors, mTOR inhibitors, estrogen and androgen antagonists, MMP inhibitors and biological response modifiers.
Still another embodiment of the present invention provides a method for treating cancer using SMAC mimetic compounds.
Accordingly, the present invention relates to SMAC mimetic peptidomimetic compounds of formula-I, useful for the treatment of cancer as a mono and combination therapy where chemotherapy fails to deliver its effect. The SMAC mimetics peptidomimetics compounds 2-9 are prepared by incorporating (2S,5R)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylic acid and compound 10 is prepared by incorporating (2S,5R)-5-phenylpyrrolidine-2-carboxylic acid residue, respectively.
The present invention provides a process for preparation of SMAC mimetic compound of Formula-I as described in Scheme A and Scheme B.
R2, R3 and R4 are each independently selected from the group consisting of H, C1-C6 alkyl and C4-C8 cycloalkyl.
(Reagent and conditions: (a) 20% TFA/DCM; (b) BocNHCH(R2′)-OH, EDCI.HCl, HOBt, DIPEA, DCM/DMF (1:1); (c) BocN(R4′)CH(R3′)-OH, EDCI.HCl, HOBt, DIPEA, DCM/DMF (1:1); (d) 10 mol % Pd-C, H2 by balloon, MeOH; (e) NH2-Ile-OBn, EDCI.HCl, HOBt, DIPEA, DCM/DMF (1:1); (f) Benzhydrylamine, IBCF, NMM, THF, −15° C.); (g) NH2-Ile-benzhydrylamide, HBTU, DIPEA, DMF)
(Reagent and conditions: (a) 20% TFA/DCM; (b) Boc-Val-OH, EDCI.HCl, HOBt, DIPEA, DCM/DMF (1:1); (c) Boc-N-Me-Ala-OH EDCI.HCl, HOBt, DIPEA, DCM/DMF (1:1); (g) H-Ile-benzhydrylamide, HBTU, DIPEA, DMF h) LiOH, THF, MeOH, water;)
Based on the process described in Scheme A, the compounds 2-9; and based on process described in Scheme B, compound 10 are prepared in the following manner;
(Reagent and conditions:(a) 20% TFA/DCM; (b) Boc-Val-OH, EDCI.HCl, HOBt, DIPEA, DCM/DMF (1:1); (c) Boc-Ala-OH, EDCI.HCl, HOBt, DIPEA, DCM/DMF (1:1); (d) 10 mol % Pd-C, H2 by balloon; (e) H-Ile-OBn, EDCI.HC1, HOBt, DIPEA, DCM/DMF (1:1); (f) Benzhydrylamine, IBCF, NMM, THF, −15° C.)
(Reagent and conditions: (a) 20% TFA/DCM; (b) Boc-Val-OH, HBTU, DIPEA, DMF;
(Reagent and conditions: (a) 20% TFA/DCM; (b) Boc-Chg-OH, HBTU, DIPEA, DMF; (c) Boc-N(Me)-Ala-OH, HBTU, DIPEA, DMF; (d) 10 mol % Pd-C, H2 by balloon, MeOH; (e) NH2-Ile-OBn, HBTU, DIPEA, DMF; (f) Benzhydrylamine, IBCF, NMM, THF, −15° C.; (g) NH2-Ile-benzhydrylamide, HBTU, DIPEA, DMF)
(Reagent and conditions: (h) LiOH, THF, Me0H, water; (g) H-Ile-benzhydrylamide, EDCI, HOBt, DIPEA, DCM; (a) 30% TFA/DCM; (b) Boc-Val-OH, EDCI, HOBt, DIPEA, DCM; (c) Boc-N-Me-Ala-OH, EDCI, HOBt, DIPEA, DCM;
SMAC mimetic peptidomimetics of Formula-I of the present invention shows strong binding affinity to BIR-2 and BIR-3 domains of the XIAP. The binding affinity is measured by in-silico experiments (
Further, the IC50 concentration of C6 against diverse cancer cell lines was determined and it was observed that the SMAC mimetic peptidomimetics of Formula-I shows potent activity against various cancer cell lines including but not limited to colon, breast, kidney, prostate, brain, ovary, pancreas, liver, melanoma, leukemia and lymphoma. (Table 2).
The SMAC mimetic C6 promotes cell death in cancer cells by turning on hallmark SMAC driven apoptotic features like cleavage of caspases and degradation of cIAP1 etc. as shown in
C6 is showing robust in-vivo anti-tumor activity by intraperitoneal, sub-cutaneous and oral route of administration as shown in
Following examples are given to support, but not limited, to the present invention.
(2S,5S)-2-benzyl 1-tert-butyl 5-(5-methylfuran-2-yl)pyrrolidine-1,2-dicarboxylate (850 mg, 2.2 mmol) was stirred in 20% TFA/DCM for 1 h. After that, the reaction mixture was concentrated to dryness under reduce pressure. This amine was then dissolved in anhydrous DMF (2 mL) and was added to the prestirred solution of Boc-Val-OH (956 mg, 4.4 mmol) and HBTU (1.7 gm, 4.4 mmol) in dry DMF (3 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (1.2 mL, 6.6 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature. After completion of reaction, water (30-40 mL) was added. Aqueous solution was extracted with ethyl acetate (3×60 mL). The combined organic layer was washed with 10% citric acid (aq.), 10% NaHCO3 (aq.) and finally with brine. The organic layer was dried with anhydrous sodium sulphate and the solvent was removed under reduced pressure to obtain the crude product, which was purified by column chromatography using 18% ethyl acetate/hexane as eluent to give the intermediate compound (2S ,5R)-benzyl 1-((S)-2-(tert-butoxycarbonylamino)-3-methylbutanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylate (II) as brownish gummy oil in 56.8% yield (605.6 mg, 1.25 mmol HRMS (ESI) (M+H)+ calculated for C27H37N2O6+=485.2646, found 485.2645.
The intermediate compound II (484.6 mg, 1 mmol) was stirred in 20% TFA/DCM for 1 h. After that, reaction mixture was concentrated to dryness under reduce pressure. This amine was then dissolved in anhydrous DMF (2 mL) and was added to the pre-stirred solution of Boc-Ala-OH (378.4 mg, 2 mmol) and HBTU (758.5 mg, 2 mmol) in dry DMF (3 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.56 mL, 3 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature.
After completion of reaction and usual work up, the intermediate compound (2S,5R)-benzyl 1-((S)-2-((S)-2-(tert-butoxyc arbonylamino)prop anamido)-3 -methylbutanoyl)-5 -(5-methylfuran-2-yl)pyrrolidine-2-carboxylate (III) was obtained as yellowish gummy oil in 65% yield (361 mg, 0.65 mmol). HRMS (ESI) (M+H)+ calculated for C30H42N3O7+=556.3017, found 556.3022.
To a stirred solution of compound III (1 mmol) in methanol (5 mL) was added 10 mol % Pd-C (0.1 mmol) and subjected to hydrogenation by purging hydrogen gas through balloon for 30 minutes. After that Pd was filtered using celite pad and filterate was concentrated in vacuo to give the free acid (2S,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonylamino)propanamido)-3-methylbutanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylic acid (IV) which was used in the next steps without further purification. After that isoleucine benzyl ester (13.3 mg, 0.06 mmol) was dissolved in anhydrous DMF (1 mL) and was added to the pre-stirred solution of compound IV (28 mg, 0.06 mmol) and HBTU (22.7 mg, 0.06 mmol) in dry DMF (1 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.034 mL, 0.18 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature. After completion of reaction, and usual work up, the protected tetrapeptide (2S,3S)-benzyl 2-((2S,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonylamino)propanamido)-3-methylbutanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)-3-methylpentanoate was obtained as yellowish gummy oil in 86% yield (34.8 mg, 0.05 mmol). HRMS (ESI) (M+H)+ calculated for C36H53N4O8+=669.3858, found 669.3865.
Protected peptide (2S,3S)-benzyl 2-((2S,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonylamino)propanamido)-3-methylbutanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)-3-methylpentanoate (67 mg, 0.1 mmol) were stirred in 20% TFA/DCM for 30 minutes. After that reaction mixture was concentrated to dryness under reduce pressure. The crude peptide was purified by reversed phase HPLC (RP-HPLC) using C-18 column and then the sample was lyophilized to give the desired peptide compound (2S,3S)-benzyl 2(2S,5R)-1(S)-2(S)-2-aminopropanamido)-3-methylbutanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)-3-methylpentanoate (2) as a white powder in 65% yield (37 mg, 0.065 mmol). The compound 2 was found to be 97% pure at 220 nm on analytical RP-HPLC. 1H NMR (500 MHz, DMSO-d6): δ/ppm=8.67 (d, 1H, J=8.2 Hz), 8.08 (br, 2H), 7.93 (d, 1H, J=8.2 Hz), 7.38-7.31 (m, 5H), 6.53 (br, 1H, J=3.1 Hz), 6.04 (brdd, 1H, J=1.0, 3.1 Hz), 5.41 (m, 1H), 5.13 (m, 2H), 4.41-4.22 (m, 3H), 3.88 (br, 1H), 2.24 (s, 3H), 2.12-1.76 (m, 6H), 1.42-1.34 (m, 1H), 1.31 (d, 3H, J=7.0 Hz), 1.23-1.12 (m, 1H), 0.86-0.77 (m, 9H), 0.61 (d, 3H, J=6.7 Hz); HRMS (ESI) (M+H)+ calculated for C31H45N4O3+=569.3334, found 569.3335.
To the solution of compound IV (50 mg, 0.12 mmol) in tetrahydrofuran (1 mL) at —15° C., was added N-methyl morpholine (17.5 μL, 0.16 mmol, 1.5 equiv). After five minutes, isobutylchloroformate (17.5 μL, 0.144 mmol, 1.2 equiv) was added to the reaction mixture. Then after five minutes, benzhydrylamine (19 μL, 0.144 mmol, 1.2 equiv) was added and the reaction mixture was stirred for additional 1 h at −15° C. After completion of reaction and usual work up, compound protected peptide tert-butyl (S)-1-((S)-1-((2S,5R)-2-(benzhydrylcarbamoyl)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-3-methyl-1-oxobutan-2-ylamino)-1-oxopropan-2-ylcarbamate (Boc-Ala-Val-Fro-bezhydrylamide) in 71% yield (53 mg, 0.085 mmol HRMS (ESI) (M+H)+ calculated for C36H47N4O6+=631.3490, found 631.3485.
Compound tert-butyl (S)-1-((S)-1-((2S,5R)-2-(benzhydrylcarbamoyl)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-3-methyl-1-oxobutan-2-ylamino)-1-oxopropan- 2-ylcarbamate (Boc-Ala-Val-Fro-bezhydrylamide) (53 mg, 0.085 mmol) were stirred in 20% TFA/DCM for 30 minutes. After that reaction mixture was concentrated to dryness under reduce pressure. The crude peptide was purified by reversed phase HPLC (RP-HPLC) using C-18 column and then the sample was lyophilized to give the desired peptide (2S,5R)-1-((S)-2-((S)-2-aminoprop anamido)-3-methylbutanoyl)-N-benzhydryl-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamide 3) as a white powder in 70% yield (32 mg, 0.06 mmol). The compound 3 was found to be 96% pure at 220 nm on analytical RP-HPLC. 1H NMR (500 MHz, DMSO-d6): δ/ppm=8.69 (d, 1H, J=8.2 Hz), 8.42 (d, 1H, J=8.3 Hz), 8.08 (br d, 2H, J=3.7 Hz), 7.35-7.21 (m, 10H), 6.52 (d, 1H, J=2.9 Hz), 6.09 (d, 1H, J=8.2 Hz), 6.0 (br d, 1H, J=2.9 Hz), 5.44 (br d, 1H, J=7.4 Hz), 4.45 (m, 1H), 4.22 (m, 1H), 3.87 (m, 1H), 2.20-2.14 (m, 1H), 2.15 (s, 3H), 2.10-1.98 (m, 2H), 1.96-1.89 (m, 1H), 1.88-1.80 (m, 1H), 1.30 (d, 3H, J=6.9 Hz), 0.77 (d, 3H, J=6.7 Hz), 0.55 (d, 3H, J=6.7 Hz); HRMS (ESI) (M+H)+ calculated for C31H39N4O4+=531.2966, found 531.2958.
Synthesis of (2S,3S)-benzyl 3-methyl-2-((2S,,5R)-1(S)-3-methyl-2-(S)-2-(methylamino)propanamido)butanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)pentanoate as referred in Scheme 2 (Compound 4)
The intermediate compound II (obtained in Scheme 1) (484.6 mg, 1 mmol) was stirred in 20% TFA/DCM for 1 h. After that reaction mixture was concentrated to dryness under reduce pressure. This amine was then dissolved in anhydrous DMF (2 mL) and was added to the pre-stirred solution of Boc-N-Me-Ala-OH (406 mg, 2 mmol) and HBTU (758.5 mg, 2 mmol) in dry DMF (3 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.56 mL, 3 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature. After completion of reaction and usual work up, the compound (2S,5R)-benzyl 1-((S)-2-((S)-2-(tert-butoxycarbonyl(methyl)amino)propanamido)-3-methylbutanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylate (V) was obtained as brownish gummy oil in 62% yield (353 mg, 0.62 mmol). HRMS (ESI) (M+H)+ calculated for C31H44N3O7+=570.3174, found 570.3407.
To a stirred solution of compound V (570 mg, 1 mmol) in methanol/tetrahydrofuran (5 mL, 1:1) was added 10 mol % Pd-C (0.1 mmol) and subjected to hydrogenation by purging hydrogen gas through balloon for 30 minutes. After that Pd was filtered using celite pad and filterate was concentrated in vacuo to give the free acid (2S,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonyl(methyl)amino)propanamido)-3-methylbutanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylic acid (VI) which was used in the next steps without further purification.
The isoleucine benzyl ester (55.5 mg, 0.25 mmol) was dissolved in anhydrous DMF (1 mL) and was added to the pre-stirred solution of compound VI (120 mg, 0.25 mmol) and HBTU (95 mg, 0.25 mmol) in dry DMF (2 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.13 mL, 0.75 mmol). After completion of reaction and usual work up the crude product, which was purified by column chromatography using 5% methanol/dichloromethane as eluent to give the compound Boc protected tetra peptide (2S,3S)-benzyl 2-((2S,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonyl(methyl)amino)propanamido)-3-methylbutanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)-3-methylpentanoate (Boc-N(Me)-Ala-Val-Fro-Ile-OBn) as brownish gummy oil in 80% yield (136 mg, 0.2 mmol). HRMS (ESI) (M+H)+ calculated for C37H55N4O8+=683.4014, found 683.4011.
Compound (2S 3S)-benzyl 2-((2S,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonyl(methyl)amino)propanamido)-3-methylbutano yl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)-3-methylpentanoate (53.5 mg, 0.08 mmol) were stirred in 20% TFA/DCM for 30 minutes. After that reaction mixture was concentrated to dryness under reduce pressure. The crude peptide was purified by reversed phase HPLC (RP-HPLC) using C-18 column and then the sample was lyophilized to give the desired compound (2S,3S)-benzyl 3-methyl-2((2S,5R)-1-((S)-3-methyl-2-((S)-2-(methylamino)propanamido)butanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)pentanoate (4) as a white powder. Yield (28 mg, 62%). The compound 4 was found to be 99% pure at 220 nm on analytical RP-HPLC.1H NMR (500 MHz, DMSO-d6): δ/ppm=8.96 (br, 1H), 8.85 (d, 1H, J=8.7 Hz), 7.93 (d, 1H, J=8.5 Hz), 7.38-7.30 (m, 5H), 6.54 (br d, 1H, J=3.2 Hz), 6.03 (brdd, 1H, J =1.0, 3.2 Hz), 5.36 (br d, 1H, J=7.7 Hz), 5.16-5.08 (m, 2H), 4.42-4.24 (m, 3H), 3.82 (br, 1H), 2.51 (s, 3H), 2.23 (s, 3H), 2.11-1.94 (m, 3H), 1.92-1.75 (m, 3H), 1.43-1.34 (m,1H), 1.33 (d, 3H, J=7.1 Hz), 1.22-1.13 (m,1H), 0.86-0.76 (m, 9H), 0.62 (d, 3H, J=6.9 Hz); HRMS (ESI) (M+H)+ calculated for C32H47N4O6+=583.3490, found 583.3482.
To the solution of intermediate compound VI (58 mg, 0.12 mmol) in tetrahydrofuran (1 mL) at −15° C., was added N-methyl morpholine (17.5 μL, 0.16 mmol, 1.5 equiv). After five minutes isobutylchloroformate (17.5 μL, 0.144 mmol, 1.2 equiv) was added to the reaction mixture. Then after five minutes, benzhydrylamine (19 μL, 0.144 mmol, 1.2 equiv) was added and the reaction mixture was stirred for additional 1 h at −15° C. After completion of reaction and usual work up the crude product was obtained, which was purified by 4% methanol/dichloromethane to give compound Boc protected peptide tert-butyl (S)-1-((S)-1-((2S,5R)-2-(benzhydrylcarbamoyl)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-3-methyl-1-oxobutan-2-ylamino)-1-oxopropan-2-yl(methyl)carbamate (Boc-N(Me)-Ala-Val-Fro-benzhydrylamide) in 75% yield (57 mg, 0.09 mmol). HRMS (ESI) (M+H)+ calculated for C37H49N4O6+=645.3647, found 645.3646.
Compound tert-butyl (S)-1-((S)-1-((2S,5R)-2-(benzhydrylcarbamoyl)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-3-methyl-1-oxobutan-2-ylamino)-1-oxopropan-2-yl(methyl)carbamate (Boc-N(Me)-Ala-Val-Fro-benzhydrylamide) (57 mg, 0.08 mmol) were stirred in 20% TFA/DCM for 30 minutes. After that reaction mixture was concentrated to dryness under reduce pressure. The crude peptide was purified by reversed phase HPLC (RP-HPLC) using C-18 column and then the sample was lyophilized to give the desired compound (2S,5R)-N-benzhydryl-1-((S)-3-methyl-2-((S)-2-(methylamino)propanamido)butanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamide (5) as a white powder in 68% yield (30 mg, 0.055 mmol).
The compound 5 was found to be more than 99% pure at 220 nm on analytical RP-HPLC. 1H NMR (500 MHz, DMSO-d6): δ/ppm=8.87 (br, 1H), 8.85 (d, 1H, J=8.9 Hz), 8.41 (d, 1H, J=8.2 Hz), 7.35-7.21 (m, 10H), 6.54 (br d, 1H, J=3.0 Hz), 6.10 (d, 1H, J =8.5 Hz), 5.99 (brdd, 1H, J =1.0, 3.0 Hz), 5.40 (br d, 1H, J =6.1 Hz), 4.47-4.43 (m, 1H), 4.27 (t, 1H, J=8.7 Hz), 3.83 (m, 1H), 2.51 (s, 3H), 2.21-2.13 (m,1H), 2.15 (s, 3H), 2.12-1.81 (m, 4H), 1.34 (d, 3H, J=6.9 Hz), 0.77 (d, 3H, J=6.7 Hz), 0.57 (d, 3H, J=6.7 Hz); HRMS (ESI) (M+H)+ calculated for C32H41iN4O4+545.3122, found 545.3116.
The isoleucine benzhdrylamide (178 mg, 0.6 mmol) was dissolved in anhydrous DMF (1 mL) and was added to the pre-stirred solution of compound VI (288 mg, 0.6 mmol) and HBTU (227.5 mg, 0.6 mmol) in dry DMF (3 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.34 mL, 1.8 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature. After completion of reaction and usual work up, the crude product thus obtained was purified by column chromatography using 5% methanol/dichloromethane as eluent to give the compound Boc protected tert-butyl (S)-1-((S)-1-((2S,5R)-2-((2S ,3S)-1-(benzhydrylamino)-3 -methyl-l-oxopentan-2-ylcarbamo y1)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-3-methyl-1-oxobutan-2-ylamino)-1-oxopropan-2-yl(methyl)carbamate as brownish gummy oil in 83% yield (379 mg, 0.5 mmol). HRMS (ESI) (M+H)+ calculated for C43H60N5O7=758.4487, found 758.4483.
Compound tert-butyl (S)-1-((S)-1(2S,5R)-24(2S ,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-ylcarbamoyl)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-3-methyl-1-oxobutan-2-ylamino)-1-oxopropan-2-yl(methyl)carbamate (250 mg, 0.32 mmol) were stirred in 20% TFA/DCM for 30 minutes. After that reaction mixture was concentrated to dryness under reduce pressure. The crude peptide was purified by reversed phase HPLC (RP-HPLC) using C-18 column and then the sample was lyophilized to give the desired Compound (2S,5R)-N-((2S,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-yl)-1-((S)-3-methyl-2-((S)-2-(methylamino)propanamido)butanoyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamide (6) as a white powder in 56% yield (119 mg, 0.18 mmol). The compound 6 was found to be 99% pure at 220 nm on analytical RP-HPLC. 1H NMR (500 MHz, DMSO-d6): δ/ppm=8.93 (d, 1H, J=8.8 Hz), 8.86 (br, 1H), 8.83 (d, 1H, J=8.4 Hz), 7.56 (d, 1H, J=8.9 Hz), 7.33-7.21 (m, 10H), 6.52 (br d, 1H, J=3.0 Hz), 6.11 (d, 1H, J=8.7 Hz), 6.03 (br d, 1H, J=2.5 Hz), 5.35 (m, 1H), 4.40-4.30 (m, 3H), 3.8 (br, 1H), 2.50 (s, 3H), 2.25 (s, 3H), 2.13-1.68 (m, 6H), 1.45-1.37 (m, 1H), 1.33 (d, 3H, J=6.9 Hz), 1.09-0.98 (m, 1H), 0.80-0.74 (m, 9H), 0.59 (d, 3H, J=6.7 Hz); HRMS (ESI) (M+H)+ calculated for C38H52N5O5=658.3963, found 658.3953.
2-benzyl 1-(tert-butyl) (2S,5S)-5-(5-methylfuran-2-yl)pyrrolidine-1,2-dicarboxylate (850 mg, 2.2 mmol) was stirred in 20% TFA/DCM for 1 h. After that, the reaction mixture was concentrated to dryness under reduce pressure. This amine was then dissolved in anhydrous DMF (2 mL) and was added to the prestirred solution of Boc-Chg-OH (1.13 gm, 4.4 mmol) and HBTU (1.7 gm, 4.4 mmol) in dry DMF (3 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (1.2 mL, 6.6 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature After completion of reaction and usual work up and purification, the intermediate compound (2S,5R)-benzyl 1-((S)-2-(tert-butoxycarbonylamino)-2-cyclohexylacetyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylate (VII) as yellowish gummy oil in 54.5% yield (629 mg, 1.2 mmol). HRMS (ESI) (M+H)+ calculated for C30H41N2O6+=525.2959, found 525.2952.
The compound VII (524.6 mg, 1 mmol) were stirred in 20% TFA/DCM for 1 h. After that reaction mixture was concentrated to dryness under reduce pressure. This amine was then dissolved in anhydrous DMF (2 mL) and was added to the prestirred solution of N-Boc-N-methylalanine (406 mg, 2 mmol) and HBTU (758.5 mg, 2 mmol) in dry DMF (3 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.56 mL, 3 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature. After completion of reaction water (10-20 mL) was added. Aqueous solution was extracted with ethyl acetate (3×30 mL). The combined organic layer was washed with 10% citric acid (aq.), 10% NaHCO3 (aq.) and finally with brine. The organic layer was dried with anhydrous sodium sulphate and the solvent was removed under reduced pressure to obtain the crude product, which was purified by column chromatography using 32% ethyl acetate/hexane as eluent to give the intermediate compound (2S,5R)-benzyl 1-((S)-2-((S)-2-(tert-butoxycarbonyl(methyl)amino)propanamido)-2-cyclohexylacetyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylate (VIII) as brownish gummy oil in 62% yield (378 mg, 0.62 mmol). HRMS (ESI) (M+H)+ calculated for C34H48N3O7+=610.3487, found 610.3378.
To a stirred solution of compound VIII (378 mg, 0.62 mmol) in methanol/tetrahydrofuran (5 mL, 1:1) was added 10 mol % Pd-C (0.06 mmol) and subjected to hydrogenation by purging hydrogen gas through balloon for 30 minutes. After that Pd was filtered using celite pad and the filtrate was concentrated in vacuo to give free acid (2S,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonyl(methyl)amino)propanamido)-2-cyclohexylacetyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylic acid (IX) which was used in the next steps without further purification. The isoleucine benzyl ester (55.5 mg, 0.25 mmol) was dissolved in anhydrous DMF (1 mL) and was added to the pre-stirred solution of Boc-N(Me)-Ala-Chg-Fro-OH (130 mg, 0.25 mmol) and HBTU (95 mg, 0.25 mmol) in dry DMF (2 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.13 mL, 0.75 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature. After completion of reaction and usual work up, the compound Boc protected tetrapeptide (2S ,3S)-benzyl 2-((2S ,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonyl(methyl)amino)propanamido)-2-cyclohexylacetyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)-3 -methylpentano ate (Boc-N(Me)-Ala-Chg-Fro-Ile-OBn) was obtained as yellowish gummy oil in 80% yield (144 mg, 0.2 mmol). HRMS (ESI) (M+H)+ calculated for C40H59N4O8+=723.4327, found 723.4325.
Compound (2S,5S)-benzyl 2-((2S,5R)-1-((S)-2-((S)-2-(tert-butoxycarbonyl(methyl)amino)propanamido)-2-cyclohexylacetyl)-5-(5 -methylfuran-2-yl)pyrrolidine- 2-carboxamido)-3-methylpentano ate (Boc-N(Me)-Ala-Chg-Fro-Ile-OBn) (58 mg, 0.08 mmol) were stirred in 20% TFA/DCM for 30 minutes. After that reaction mixture was concentrated to dryness under reduce pressure. The crude peptide was purified by reversed phase HPLC (RP-HPLC) using C-18 column and then the sample was lyophilized to give the desired compound (2S,3S)-benzyl 2-((2S,5R)-1-((S)-2-cyclohexyl-2((S)-2-(methylamino)propanamido)acetyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamido)-3-methylpentanoate 7 as a white powder in 62% yield (28 mg, 0.05 mmol). The compound 7 was found to be 98% pure at 220 nm on analytical RP-HPLC. 1H NMR (500 MHz, DMSO-d6): δ/ppm=8.88 (br, 1H), 8.79 (d, 1H, J=8.3 Hz), 7.86 (d, 1H, J=8.3 Hz), 7.37-7.32 (m, 5H), 6.51 (br d, 1H, J=3.0 Hz), 6.05 (brdd, 1H, J=1.0, 3.0 Hz), 5.34 (m, 1H), 5.17-5.08 (m, 2H), 4.42-4.32 (m, 3H), 3.83-3.79 (m, 1H), 2.50 (s, 3H), 2.24 (s, 3H), 2.09-1.86 (m, 4H), 1.83-1.76 (m, 1H), 1.70-1.41 (m, 7H), 1.33 (d, 3H, J =6.9 Hz), 1.20-1.12 (m, 1H), 1.06-0.92 (m, 3H), 0.86-0.77 (m, 7H), 0.55-0.46 (m, 1H); HRMS (ESI) (M+H)+ calculated for C35H51N4O6+=623.3803, found 623.3800.
Synthesis of (2S,5R)-N-benzhydryl-14(S)-2-cyclohexyl-24(S)-2-(methylamino)propanamido)acetyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamide as referred in Scheme 3 (Compound 8)
To the solution of intermediate compound IX (62.4 mg, 0.12 mmol) in tetrahydrofuran (1 mL) at −15° C. was added N-methyl morpholine (17.5 μL, 0.16 mmol, 1.5 equiv). After five minutes isobutylchloroformate (17.5 μL, 0.144 mmol, 1. 2 equiv) was added to the reaction mixture. Then after five minutes benzhydrylamine (19 μL, 0.144 mmol, 1.2 equiv) was added and the reaction mixture was stirred for additional 1 h at −15° C. After completion of reaction and usual work up compound Boc protected tetrapeptide tert-butyl (S)-1-((S)-2-((2S ,5R)-2-(benzhydrylcarbamoyl)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-1-cyclohexyl-2-oxoethylamino)-1-oxopropan-2-yl(methyl)carbamate was obtained in 67% yield (55 mg, 0.08 mmol). HRMS (ESI) (M +H)+ calculated for C40H53N4O6+=685.3960, found 685.3939.
Compound tert-butyl (S)-1-((S)-2-((2S,5R)-2-(benzhydrylcarbamoyl)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-1-cyclohexyl-2-oxoethylamino)-1-oxopropan-2-yl(methyl)carbamate (55 mg, 0.08 mmol) were stirred in 20% TFA/DCM for 30 minutes. After that reaction mixture was concentrated to dryness under reduce pressure. The crude peptide was purified by reversed phase HPLC (RP-HPLC) using C-18 column and then the sample was lyophilized to give the desired compound (2S,5R)-N-benzhydryl-1(S)-2-cyclohexyl-2(S)-2-(methylamino)propanamido)acetyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxamide (8) as a white powder in 62.5% yield (29 mg, 0.05 mmol). The compound 8 was found to be 99% pure at 220 nm on analytical RP-HPLC. 1H NMR (500 MHz, DMSO-d6): δ/ppm=8.88 (br, 1H), 8.81 (d, 1H, J=8.0 Hz), 8.30 (d, 1H, J=8.4 Hz), 7.36-7.21 (m, 10H), 6.51 (br d, 1H, J =3.1 Hz), 6.10 (d, 1H, J=8.1 Hz), 6.01 (brdd, 1H, J=1.0, 3.1 Hz), 5.38 (m, 1H), 4.46 (m, 1H), 4.36 (t, 1H, J=8.5 Hz), 3.82 (m, 1H), 2.50 (s, 3H), 2.21-1.89 (m, 4H), 2.14 (s, 3H), 1.70-1.39 (m, 5H), 1.33 (d, 3H, J=7.0 Hz), 1.13-0.89 (m, 4H), 0.79-0.69 (m, 1H), 0.51-0.42 (m, 1H); HRMS (ESI) (M 30 H)+ calculated for C35H45N4+=585.3435, found 585.3427.
Synthesis of (2S,5R)-N-2S,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-yl)-1(S)-2-cyclohexyl-2-((S)-2-(methylamino)propanamido)acetyl)-5-(5- methylfuran-2-yl)pyrrolidine-2-carboxamide (Compound 9)
The (2S,3S)-2-amino-N-benzhydryl-3-methylpentanamide (60 mg, 0.2 mmol) was dissolved in anhydrous DMF (1 mL) and was added to the pre-stirred solution of (2S,5R)-1-((S)-2-((S)-2-(tert-butoxyc arbonyl(methyl)amino)propanamido)-2-cyclohexylacetyl)-5-(5-methylfuran-2-yl)pyrrolidine-2-carboxylic acid (104 mg, 0.2 mmol) and HBTU (75.8 mg, 0.2 mmol) in dry DMF (1 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.11 mL, 0.6 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature. After completion of reaction and usual work up, the compound Boc protected peptide tert-butyl (S)-1-((S)-2-((2S,5R)-2-((2S,3S)-1-(benzhydrylamino)-3 -methyl-1-oxopentan-2-ylcarbamoyl)-5-(5 -methylfuran-2-yl)pyrrolidin-1-yl)-1-cyclohexyl-2-oxoethylamino)-1-oxopropan-2-yl(methyl)carb amate was obtained as brownish gummy oil in 85% yield (135 mg, 0.17 mmol). HRMS (ESI) (M+H)+ calculated for C46H64N5O7+=798.4800, found 798.4817.
Compound tert-butyl (S)-1(S)-2(2S,5R)-2-((2S,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-ylcarbamoyl)-5-(5-methylfuran-2-yl)pyrrolidin-1-yl)-1-cyclohexyl-2-oxoethylamino)-1-oxopropan-2-yl(methyl)carbamate (80 mg, 0.1 mmol) were stirred in 20% TFA/DCM for 30 minutes. After that, reaction mixture was concentrated to dryness under reduce pressure. The crude peptide was purified by reversed phase HPLC (RP-HPLC) using C-18 column and then the sample was lyophilized to give the desired compound (2S,5R)-N-((2S,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-yl)-1-((S)-2-c yclohexyl-24(S)-2-(methylamino)prop anamido)acetyl)-5 -(5-methylfuran-2-yl)pyrrolidine-2-carboxamide (9) as a white powder in 60% yield (41 mg, 0.06 mmol). The compound 9 was found to be 98% pure at 220 nm on analytical RP-HPLC. 1H NMR (500 MHz, DMSO-d6): δ/ppm=8.92 (d, 1H, J=8.6 Hz), 8.80 (br, 1H), 8.75 (d, 1H, J=8.0 Hz), 7.52 (br d, 1H, J=9.1 Hz), 7.33-7.22 (m, 10H), 6.48 (br d, 1H, J=3.0 Hz), 6.10 (d, 1H, J=8.4 Hz), 6.04 (brdd, 1H, J=1.0, 3.0 Hz), 5.33 (m, 1H), 4.43-4.38 (m, 3H), 3.82 (br m, 1H), 2.50 (s, 3H), 2.26 (s, 3H), 2.14-1.96 (m, 4H), 1.76-1.37 (m, 8H), 1.33 (d, 3H, J =6.8 Hz), 1.09-0.98 (m, 2H), 0.97-0.86 (m, 2H), 0.79-0.72 (m, 7H), 0.54-0.44 (m, 1H); HRMS (ESI) (M+H)+ calculated for C41H56N5O5+=698.4276, found 698.4245.
Synthesis of (2S,5R)-N-42S,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-yl)-1-(methyl-L-alanyl-L-alanyl)-5-phenylpyrrolidine-2-carboxamide as referred in Scheme 4 (Compound 10)
In a round bottom flash, compound 1-(tert-butyl) 2-methyl (2S,5R)-5-phenylpyrrolidine-1,2-dicarboxylate (3.089 gm, 10.127 mmol) was taken in 50 ml mixture of Methanol/Water (10:1). LiOH (890 mg, 20.255 mmol) was added subsequently in the reaction mixture at 0° C. The reaction mixture was monitored by the TLC. After completion of the reaction, 50 ml of water was added in the reaction, evaporate the organic solvents from the reaction mixture. Subsequently ethyl acetate and water was added, and organic layer was separated out which contain the impurities. Water layer was acidified with citric acid, and ethyl acetate was added in that layer. Organic layer was separated and washed with brine and dried over anhydrous Na2SO4. Organic layer was evaporated under reduced pressure to obtain free acid as white solid. Crude acid was directly used for the next step without further purification. NH2-Ile-benzhydrylamide (4.42 gm, 14.948 mmol) was dissolved in dry DCM (15 mL) and was added to the pre-stirred solution of Crude acid (2.9 gm, 9.96 mmol), EDC.HCl (5.71 g, 29.896 mmol) and HOBt (4.035 g, 29.896 mmol) in dry DCM (35 mL) at 0° C. and under nitrogen 15 atmosphere followed by addition of DIPEA (5.17 mL, 29.896 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature After completion of reaction and usual work up, the crude product was purified by column chromatography using silica gel (40% Ethylacetate/Hexane)) to give title compound (2S,5R)-tert-butyl 2-((2S ,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-ylcarbamoyl)-5-phenylpyrrolidine-1-carboxylate (XI) as white solid (4.657 gm, 8.184 mmol, yield 82%).
To the compound XI (4.45 gm, 7.82 mmol), 30% TFA/DCM (25 mL) [3m1/mM viz. 1 ml TFA and 2 ml of DCM/mM] were added at 0° C. and reaction was stirred for additional 1 h at room temperature. After that the reaction mixture was concentrated to dryness under reduce pressure and to this DCM (150 mL) was added which was washed with 10% Na2CO3 (aq.). The organic layer was dried with anhydrous sodium sulphate and the solvent was removed under reduced pressure, crude amine was afforded as white solid (3.36 gm, 7.036 mmol, yield 90%). This crude amine (600 mg, 1.27 mmol) was dissolved in dry DCM (10 mL) and was added to the pre-stirred solution of Boc-NH-valine (692 mg, 3.195 mmol), EDC.HC1 (1.342 g, 7.034 mmol) and HOBt (950 mg, 7.034 mmol) in dry DCM (25 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (1.22 mL, 7.034 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature After completion of reaction and usual work up, the crude product was purified by column chromatography using silica gel (40% EA/Hexane) to give title compound tert-butyl (S)-1-((2S ,5R)-2-((2S,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-ylcarbamoyl)-5-phenylpyrrolidin-1-yl)-3 -methyl-1-oxobutan-2-ylcarbamate (XII) as white solid (723 gm, 1.082 mmol, yield 85%).
To the compound XII (700 mg, 1.047 mmol), 30% TFA/DCM (6 mL) [3 m/mM viz. 1 ml TFA and 2 ml of DCM/mM] were added at 0° C. and reaction was stirred for additional 1 h at room temperature. After that, the reaction mixture was concentrated to dryness under reduce pressure and to this DCM (30 mL) was added which was washed with 10% Na2CO3 (aq.). The organic layer was dried with anhydrous sodium sulphate and the solvent was removed under reduced pressure, crude amine was afforded as white solid (740 mg, 0.827 mmol, yield 80%). This crude amine (430 mg, 0.757 mmol) was dissolved in dry DCM (2 mL) and was added to the pre-stirred solution of Boc-val-OH (385 mg, 1.892 mmol), EDC.HCl (1.05 g, 4.163 mmol) and HOBt (563 mg, 4.163 mmol) in dry DCM (8 mL) at 0° C. under nitrogen atmosphere followed by addition of DIPEA (0.97 mL, 4.163 mmol). The reaction mixture was further stirred for additional 4-6 h at room temperature After completion of reaction and usual work up, the crude product was purified by column chromatography using silica gel (40% EA/Hexane) to give title compound tert-butyl (S)-1-((S)-1-((2S,5R)-2-((2S ,3S)-1-(benzhydrylamino)-3-methyl-1-oxopentan-2-ylcarbamoyl)-5-phenylpyrrolidin-1-yl)-3-methyl-l-oxobutan-2-ylamino)-1-oxopropan-2-yl(methyl)carbamate (XIII) as white solid (477 gm, 0.633 mmol, yield 84%).
To the compound XIII (430 mg, 0.571 mmol), 30% TFA/DCM (6 mL) [3 ml/mM viz. 1 ml TFA and 2 ml of DCM/mM] were added at 0° C. and reaction was stirred for additional 1 h at room temperature. After that the reaction mixture was concentrated to dryness under reduce pressure and to this DCM (30 mL) was added which was washed with 10% Na2CO3 (aq.). The organic layer was dried with anhydrous sodium sulphate and the solvent was removed under reduced pressure, crude product was purified by column chromatography using silica gel (8% MeOH/DCM) to give title compound (2S,5R)-N-((2S,3S)-1-(benzhydrylamino)-3-methyl-l-oxopentan-2-yl)-1-((S)-3-methyl-2-((S)-2-(methylamino)propanamido)butanoyl)-5-phenylpyrrolidine-2-carboxamide (10) as white solid (326 mg, 0.499 mmol, yield 87%). ESIMS (M+H)+ calculated for C39H52N5O4=654.4 found 654.6
The SMAC mimetics 1-9 were tested for their ability to displace the fluorescent labeled peptide AVPIAQK(FAM)-OH from XIAP BIR2 or XIAP BIR3 protein. The dose dependent binding experiment were then carried out by sequentially increasing the concentration of SMAC mimetic compounds at constant concentration of fluorescent labeled peptide and XIAP BIR2 or XIAP BIR3 protein. IC5- values were determined from the plot draw by prism software using nonlinear least-squares analysis. The Ki values of the SMAC mimetics were calculated which was based upon the measured IC50 values, the Kd value between tracer AVPIAQK(FAM)-OH and XIAP BIR2 or XIAP BIR3 complex, and the concentrations of the protein and tracer in the competition assay by using the web based program which are freely accessed at http://sw16.im.med.umich.edu/software/calc_ki/.In-silico.
SMAC mimetics bind to BIR2 and BIR3 domains of XIAP as determined by FPA. Binding isotherms were plotted between FP reading versus log values of protein concentration in nM. The data was analysed using GraphPad prism and Kd values were determined using Boltzmann-sigmoidal non-linear regression curve fitting. First, the Kd values for binding of fluorescent labelled peptide with XIAP BIR2 and XIAP BIR3 were determined to assess the exact Ki values for each molecule bindings towards BIR2/3 domains are shown in Table-1.
In vitro cytotoxic activities of different compounds were assessed by using standard SRB assay in different cells. The absorbance of the treated and untreated cells was measured on a multi-well scanning spectrophotometer (Epoch Microplate Reader, Biotek, USA) at a wavelength of 510 nm. Percent growth inhibition was calculated by using the formula [100-(Absorbance of compound treated cells/Absorbance of untreated cells)] X 100.
SMAC mimetics promotes tumor cell selective cytotoxic effects. SW 620, HT 29, HCT 116 and VERO cells were treated with series of Smac mimetics at 10 μM dose for 48 hours and cytotoxicity was measured by SRB assay. Percent growth inhibition was tabulated in Table 1 as provided above. As C6 had shown robust in-vitro cytotoxic effect against tumor cells but not to VERO cells, we determined IC50 value of C6 against different types of cancer cell lines. ICso values are represented in Table 2. We also assessed In Silico Molecular Docking Analysis of C6 (
Apoptosis array was performed by using Proteome Profiler Human Apoptosis Array Kit (ARY009) from R&D Systems following the manufacturer's instructions. The detailed assay procedure was followed. The images were captured by the gel documentation system (Bio-Rad chemidoc XRS plus), while ImageJ software (NIH) was used for analysis and quantification. Plotly software was used for heatmap generation (Montreal, Canada).
It was observed that compound C6 promotes smac driven apoptotic features as observed by right shift of histogram overlays show the Annexin-V positive cells (
Further, C6 treatment drives SMAC mediated hall mark apoptotic features as observed by cleavage of PARP and Caspase-3 and degradation of cIAP-1 in treated cells as compared to control (
The clonogenic colony formation assay was done on single-cell suspension. Briefly, cells were plated in complete McCoy's medium into 12-well plates and 24 hours later, were treated with different agents at different doses either alone or in combination. The cells were cultured for two weeks with renewing the media every 3rd day. The plates were washed with PBS and fixed with ice-cold methanol followed by staining with 0.5% crystal violet in methanol for 30 min. Excess stain was removed by washing with water thoroughly and plates were allowed to dry. Representative images were captured in the gel documentation system (Bio-Rad chemidoc XRS plus) while ImageJ software (NIH) was used for analysis and quantification to monitor single cell colony formation efficiency under the different treatment combinations.
Inhibition of apoptosis by Pan caspase inhibitor Z-VAD-FMK markedly rescues cytotoxic phenotype of C6 as observed by colony formation assay and confirmed that C6 induces apoptotic cell death in cancer cells (
All the animals were maintained in a pathogen-free facility under a day—night cycle.
Following our well-established colon cancer xenograft models, 2×106 cells (SW 620 and HCT 116) or 0.5×106 cells (HCT 116) in 100 μl PBS were subcutaneously inoculated into the flanks of the left/and or right hind leg of each 4-6 weeks old nude Crl: CD1-Foxnlnu mice. Mice were randomly assigned to groups by a blinded independent investigator. Throughout the study, the tumor was measured with an electronic digital caliper at a regular interval, and the tumor volume was calculated using standard formula V=Π/6×a2×b, where ‘a’ is the short and ‘b’ is the long tumor axis. At the end of the experiment, mice were sacrificed, and subcutaneous tumors were dissected for further studies. Parts of harvested tumors were minced into small pieces with sterile forceps and scissors and homogenized for lysate preparation.
Utilizing the cisplatin resistant SW-620 xenograft model, we determined the in vivo efficacy of C6 and observed that it has potent anti tumor efficacy against the same model (
SIF, SGF and other stability studies were performed by following standard protocol. LC-MS/MS method was developed for C6: Intravenous group (C6, 4 mg/kg), Subcutaneous group (C6, 30 mg/kg), Oral group (C6, 30 mg/kg). Mice were administered their respective doses according to body weight by intravenous (lateral vein), Subcutaneous route and Oral respectively. Blood samples were collected at 0.083, 0.25, 0.5, 0.75, 1, 2, 4, 8, 12, 24 and 48 hours. Plasma was separated and processed for analysis. For pharmacokinetic analysis, plasma concentration versus time data were plotted and analyzed by non-compartmental analysis method using WinNonlin (Pharsight, Mountain View, CA) software.
C6 is quite stable in SIF, SGF, plasma, MLM, HLM as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 202011055682 | Dec 2020 | IN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IN2021/051182 | 12/17/2021 | WO |
