Patent ID: 8399500

Claim:
A method for synthesizing a derivative of following formula (I): or a physiologically acceptable salt thereof, a tautomer, a stereoisomer or a mixture of stereoisomers in all proportions; for which: R 1 and R 2 represent, independently of each other, a hydrogen atom or a (C 1 -C 4 ) alkyl group, at least one of the R 1 and R 2 groups representing a hydrogen atom; and R 3 , R 4 and R 5 represent, independently of each other, a (C 1 -C 4 ) alkyl group; comprising the following successive steps: (i) cleavage reaction of a compound of betaine type of following formula (II): or a physiologically acceptable salt, a tautomer, a stereoisomer or a mixture of stereoisomers in all proportions; for which: represents R 1 , R 2 , R 3 , R 4 and R 5 are as defined above, R 6 represents a hydrogen atom or a (C 1 -C 4 ) alkyl or —CO—((C 1 -C 4 )alkyl) group, and R 7 represents a hydrogen atom or a (C 1 -C 4 ) alkyl group; in the presence of a thiol, at a temperature above or equal to 60° C., to give a compound of formula (I); and (ii) separation of the compound of formula (I) obtained at the preceding step (i) from the reaction medium.