IMPROVED PROCESS FOR SYNTHESIZING FUNCTIONALIZED MERCAPTANS

Abstract

The present invention relates to a process for synthesizing functionalized mercaptans essentially in the absence of oxygen, and also to a composition making it possible in particular to implement this process. Said functionalized mercaptans are of the following formula (I):

Description

Claims

1. Process for synthesizing at least one functionalized mercaptan of the following general formula (I): in which,R1 and R7, which are identical or different, are a hydrogen atom or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon chain of 1 to 20 carbon atoms which may comprise one or more heteroatoms;X is chosen from -C(=O)-, -CH2- or -CN;R2 is: (i) either absent when X represents -CN,(ii) or a hydrogen atom,(iii) or -OR3, R3 being a hydrogen atom or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon chain of 1 to 20 carbon atoms which may comprise one or more heteroatoms,(iv) or -NR4R5, R4 and R5, which are identical or different, being a hydrogen atom or an aromatic or nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon chain of 1 to 20 carbon atoms which may comprise one or more heteroatoms;n is equal to 1 or 2; and * represents an asymmetric carbon; said process comprising the steps of: a) provision of at least one compound of the following general formula (II): in which *, R1, R2, R7, X and n are as defined for formula (I) and G represents either (i) R6-C(O)-O-, or (ii) (R70)(R8O)-P(O)-O-, or (iii) R9O-SO2-O-; withR6 being a hydrogen atom or a linear, branched or cyclic, saturated or unsaturated hydrocarbon chain of 1 to 20 carbon atoms which may comprise one or more aromatic groups and may be substituted by one or more groups chosen from -OR10, (=O), -C(O)OR11, -NR12R13;R10, R11, R12 and R13 being independently chosen from: H or a linear, branched or cyclic, saturated or unsaturated hydrocarbon chain of 1 to 20 carbon atoms;R7 and R8, which are identical or different, being a proton, an alkali metal, an alkaline earth metal or an ammonium;R9 being chosen from a proton, an alkali metal, an alkaline earth metal or an ammonium;b) provision of at least one hydrosulfide salt and/or sulfide salt or H2S;c) reaction between said at least one compound of formula (II) and said at least one hydrosulfide and/or sulfide salt or H2S in the presence of at least one enzyme chosen from sulfhydrylases, and preferably a sulfhydrylase associated with said compound of formula (II); said reaction being performed essentially in the absence of oxygen, preferably in the absence of oxygen;d) obtaining of at least one functionalized mercaptan of formula (I);e) optional separation of said at least one functionalized mercaptan of formula (I) which is obtained in step d); andf) optional additional functionalization and/or optional deprotection of the functionalized mercaptan of formula (I) which is obtained in step d) or e); and wherein steps a) and b) are optionally performed simultaneously.

2. Synthesis process according to claim 1, wherein step c) takes place in a reactor in which the reaction mixture comprises less than 0.0015% oxygen by weight relative to the total weight of the reaction mixture and/or the gas phase contained in the gas headspace of the reactor comprises less than 21% oxygen by volume relative to the total volume of said gas phase.

3. Synthesis process according to claim 1, wherein the hydrosulfide salt and/or sulfide salt or H2S is in excess relative to the compound of formula (II), preferably during step c).

4. Synthesis process according to claim 1, wherein the molar ratio [hydrosulfide salt and/or sulfide salt] / [compound of formula (II)] or H2S/compound of formula (II) is comprised between 1.5 and 10, preferentially between 2 and 8, and even more preferentially between 3.5 and 5, limits included, preferably during step c).

5. Synthesis process according to claim 1, wherein said at least one hydrosulfide and/or sulfide salt is chosen from the group consisting of: ammonium hydrosulfide, alkali metal hydrosulfides, alkaline earth metal hydrosulfides, alkali metal sulfides and alkaline earth metal sulfides.

6. Synthesis process according to claim 1, wherein the pH of the reaction medium in step c) is comprised between 4 and 9, for example between 5 and 8, preferably between 6 and 7.5, and more particularly between 6.2 and 7.2, limits included.

7. Synthesis process according to claim 1, wherein the compound of formula (II) is chosen from the group consisting of: O-phospho-L-homoserine, O-succinyl-L-homoserine, O-acetyl-L-homoserine, O-acetoacetyl-L-homoserine, O-propio-L-homoserine, O-coumaroyl-L-homoserine, O-malonyl-L-homoserine, O-hydroxymethylglutaryl-L-homoserine, O-pimelyl-L-homoserine and O-sulfato-L-homoserine, preferably O-acetyl-L-homoserine.

8. Process according to claim 1, wherein said compound of formula (II) is O-acetyl-L-homoserine, the enzyme used is O-acetyl-L-homoserine sulfhydrylase and the functionalized mercaptan of formula (I) is L-homocysteine.

9. Process according to claim 1, wherein said sulfhydrylase is a transferase of the E.C.2. type.

10. Composition, preferably solution, comprising: a compound of formula (II) as defined in claim 1;a sulfhydrylase, preferably a sulfhydrylase associated with the compound of formula (II); andammonium hydrosulfide NH4SH or H2S in excess.