A method for preparing 2-hydroxybutyrolactone from a compound, or from its salt or its oligomers, said compound fitting formula CH 3 -S-CH 2 CH 2 CR1R2R3 wherein R1 represents H R2 represents a group selected from OH; OR4 and OCOR4 wherein R4 represents a group selected from linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, and aryl groups having from 6 to 10 carbon atoms, optionally substituted with substituent(s) selected from linear or branched alkyl groups having from 1 to 10 carbon atoms halogens and hydroxyl, amino, nitro and alkoxy groups having from 1 to 10 carbon atoms; and OSiRR'R" wherein R, R' and R" are selected independently of each other from linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, aryl groups having from 6 to 10 carbon atoms, optionally substituted with substituent(s) selected from linear or branched alkyl groups having from 1 to 10 carbon atoms, or R1 and R2 represent together =O, R3 represents COOH or a COOR5 wherein R5 represents a group selected from linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, benzyl groups and benzyl groups substituted with one or two substituents selected from linear or branched alkyl groups having from 1 to 10 carbon atoms, halogens and hydroxyl, amino, nitro and alkoxy groups having from 1 to 10 carbon atoms, or R3 represents a cyano group, method according to which a sulfonium of said compound is obtained, said sulfonium fitting the formula [CH 3][CH 2 CH 2 CR1R2CR3][CR6R7R8]S + X - By reacting with an agent fitting formula [CR6R7R8]X wherein R1, R2 and R3 have the above definition, and R6 and R7 are selected independently of each other from H, linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, and aryl groups having from 6 to 10 carbon atoms optionally substituted with substituent(s) selected from linear or branched alkyl groups having from 1 to 10 carbon atoms, halides and hydroxyl, amino, nitro and alkoxy groups having from 1 to 10 carbon atoms; R8 is selected from H, linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, aryl groups having from 6 to 10 carbon atoms, optionally substituted with substituent(s) selected from linear or branched alkyl groups having from 1 to 10 carbon atoms, and attractor groups notably those comprising a function selected from acid, ester, cyano functions and X represents a counter-ion, and the thereby obtained sulfonium is hydrolyzed in 2,4-dihydroxybutyric acid or its salt, and 2,4-dihydroxybutyric acid or its salt is cyclized into 2-hydroxybutyrolactone. R1 represents H R2 represents a group selected from OH; OR4 and OCOR4 wherein R4 represents a group selected from linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, and aryl groups having from 6 to 10 carbon atoms, optionally substituted with substituent(s) selected from linear or branched alkyl groups having from 1 to 10 carbon atoms halogens and hydroxyl, amino, nitro and alkoxy groups having from 1 to 10 carbon atoms; and OSiRR'R" wherein R, R' and R" are selected independently of each other from linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, aryl groups having from 6 to 10 carbon atoms, optionally substituted with substituent(s) selected from linear or branched alkyl groups having from 1 to 10 carbon atoms, or R1 and R2 represent together =O, R3 represents COOH or a COOR5 wherein R5 represents a group selected from linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, benzyl groups and benzyl groups substituted with one or two substituents selected from linear or branched alkyl groups having from 1 to 10 carbon atoms, halogens and hydroxyl, amino, nitro and alkoxy groups having from 1 to 10 carbon atoms, or R3 represents a cyano group, method according to which a sulfonium of said compound is obtained, said sulfonium fitting the formula [CH 3][CH 2 CH 2 CR1R2CR3][CR6R7R8]S + X - By reacting with an agent fitting formula [CR6R7R8]X wherein R1, R2 and R3 have the above definition, and R6 and R7 are selected independently of each other from H, linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, and aryl groups having from 6 to 10 carbon atoms optionally substituted with substituent(s) selected from linear or branched alkyl groups having from 1 to 10 carbon atoms, halides and hydroxyl, amino, nitro and alkoxy groups having from 1 to 10 carbon atoms; R8 is selected from H, linear, cyclic or branched alkyl groups having from 1 to 10 carbon atoms, aryl groups having from 6 to 10 carbon atoms, optionally substituted with substituent(s) selected from linear or branched alkyl groups having from 1 to 10 carbon atoms, and attractor groups notably those comprising a function selected from acid, ester, cyano functions and X represents a counter-ion, and the thereby obtained sulfonium is hydrolyzed in 2,4-dihydroxybutyric acid or its salt, and 2,4-dihydroxybutyric acid or its salt is cyclized into 2-hydroxybutyrolactone.