Patent Application
20050085452
This invention provides a novel process for the synthesis of pharmacologically active Z/E stereoisomeric mixture of guggulsterones in high purity. Guggulsterones consists of a mixture of Z-guggulsterone, which is 4,17(20)-trans-pregnadiene-3,16-dione and E-guggulsterone, which is 4,17(20)cis-pregnadiene-3,16-dione. This mixture of stereoisomeric pregnadiene-3,16-diones may be in any relative ratio and is herein after referred as (Z/E)-guggulsterones.
Guggul resin obtained from the tree Commiphora mukul belonging to the family Burseraceae is known as guggulu in Sanskrit and guggul in Hindi. Indian Patent Specification No. 148265 describes a process for extraction of guggulipid from guggul resin by ethyl acetate. Guggulipid is found to contain two stereoisomers of guggulsterones. Medicinal activity of the plant extract is similar to the well known drug clofibrate but without its side effects.
Isolation of Z and E-guggulsterones from the oleo-resin or gum of the tree Commiphora mukul has also been reported in Tetrahedron, 1972, 28, 2341-52 by Sukh Dev, et al. A process for obtaining pharmacologically active fraction, guggulipid, has also been disclosed in the U.S. Pat. No. 5,273,747, 1993. Guggulsterones have been shown to exhibit beneficial action in the management of ischaemic heart diseases, hypolipidaemic and anti-inflammatory action with no side effects.
However, the tree Commiphora mukul having the biologically active lipid is not easily available and a large number of trees are to be harvested for the resin. The naturally occurring resin has only a low concentration of the active guggulsterones. Further, preparation of dosage forms such as tablets or capsules from the oleo-resin extract poses problems due to its gummy nature.
European patent No. EP. 0 447 706, discloses a four step procedure for the synthesis of Z and E-guggulsterones. This process includes the reduction of an α,β-unsaturated ketone of 16-dehydropregnenolone acetate (16-DPA) with lithium aluminium hydride in dry tetrahydrofuran. The second step is an acid catalysed isomerisation using acetic anhydride, acetic acid and P-toluene sulphonic acid. The reagents and solvents used in this process are expensive and the process is tedious.
The object of this invention is to provide an improved process for the production of pharmacologically active synthetic Z/E-guggulsterones, which is cost effective. The product obtained has high purity.
The present invention is an improved process for the preparation of pharmacologically active synthetic Z/E-guggulsterones in three steps. The process comprises the reaction of 16-dehydropregnenolone acetate with hydrogen peroxide in a polar solvent in the presence of a base to give 16,17-epoxy-3-hydroxy-5-pregnen-20-one. This is subjected to Wolff-Kishner reduction and elimination under Huang-Minlon conditions with hydrazine hydrate in a polar solvent and/or in the presence of a base to give a diastereomeric mixture of 5,17(20)pregnadiene-3,16-diol. Oppenauer oxidation of the diol mixture in an aromatic solvent in the presence of a catalyst using a hydrogen acceptor produces Z/E-guggulsterones, which is isolated and subjected to further purification.
This invention relates to a process for synthesising pharmacologically active Z/E-guggulsterones which comprises reacting 16-dehydropregnenolone acetate with hydrogen peroxide in the presence of a base to give the corresponding epoxide, reducing said epoxide with hydrazine hydrate to produce a diastereomeric mixture of 5,17(20)pregnadiene-3,16-diol, oxidizing said diastereomeric mixture with a hydrogen acceptor in the presence of a catalyst to produce Z/E-gugguisterones which is isolated and purified in a known manner.
The reaction in the first two stages may be carried out in a polar solvent such as methanol, ethanol, isopropyl alcohol t-butanol and mixtures thereof. Non-polar solvents such as tetrahydrofuran, dioxane, ether and mixtures thereof may also be used. Aromatic solvents such as toluene, xylenes and chlorobenzene may also be used in the oxidation step. Catalyst used in the reaction may be selected from aluminium isopropoxide, aluminium isobutoxide, aluminium phenoxide or aluminium tertiary butoxide.
The hydrogen acceptor in the oxidation stage may be acetone, ethyl methyl ketone, diethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, cycloheptanone, acetophenone or benzophenone.
Purification of the diastereomeric mixture of guggulsterones is carried out by chromatographic separation on a silica gel column using polar and non-polar solvents or mixtures thereof. Reversed phase silica column separation may also be used for purifying the product. The polar solvents used for elution are ethanol, methanol or water and non-polar solvents include hexane, cyclohexane, toluene, chloroform, ethyl acetate or acetone and mixtures thereof.
The reaction scheme is shown below.
The following example illustrates the present invention but do not limit the scope thereof.
To a solution of 16-dehydropregnenolone acetate (4.0 Kg) in alcohol (100 L) was added hydrogen peroxide (1.6 L) followed by dropwise addition of 4N sodium hydroxide solution for 1 hr. The reaction mixture was stirred at 5-15° C. for 12 hrs and the solid obtained was filtered and dried to give compound of formula 2 in the reaction scheme (Yield: 3.52-3.66 Kg, 95-99%, m.p. 194-196° C.).
To a solution of the 16,17-epoxy-3-hydroxypregn-5-en-20-one (2.0 Kg) in hydrazine hydrate (7.2 L) was added potassium hydroxide (0.7 Kg) and the mixture was heated for 4 hrs. The cooled reaction mixture was diluted with ice cold water and acidified with dilute HCl. The solid obtained was filtered and washed with water and dried to give the compound of formula 3 shown in the reaction scheme (yield: 1.53-1.82 Kg, 80-95%, m.p. 168-172° C.).
Alternate Route:
To a solution of the 16,17-epoxy-3-hydroxy pregn-5-en-20-one (91 g) in alcohol (2.0 L) was added hydrazine hydrate (155 mL) and the mixture was refluxed for 6 hrs. Solvent was removed at reduced pressure and diluted with cold water. The solid separated was filtered, washed with cold water and dried to give compound of the formula 3 shown in the reaction scheme (yield: 69.7-82.8 g, 80-95%, m.p. 168-170° C.).
A solution of 5,17(20)-pregnadiene-3,16-diol (0.8 Kg) in toluene (30.0 L), cyclohexanone (4.0 L) and aluminium isopropoxide (0.75 Kg) were refluxed for 4 hrs. The reaction mixture was cooled, acidified with 10% sulfuric acid (5.0 L) and separated the layers. The aqueous layer was extracted twice with toluene (2.0 L). The combined toluene layer was washed sequentially, with water (2.0 L), 10% NaHCO3 (2.0 L) and water (2.0 L). Toluene was distilled off under vaccum to give a gummy residue, which was chromatographed over silica gel column eluting using mixtures of pet.ether-ethyl acetate for elution to give the Z/E-guggulsterones (Yield: 0.39-0.71 Kg, 50-90%, m.p. 174-178° C.). The ratio of Z to E in the final product was found to be in the range of 10 to 0.1 and the purity of gugguisterones is >99% by HPLC.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IN02/00181 | WO |
