Patent ID: 7420087

Claim:
A method of preparing diastereoisomers and enantiomers of 4-hydroxyisoleucine and derivatives thereof of general formula I in which R 1 and R 2 represent a hydrogen atom or one of R 1 or R 2 represents a hydrogen atom and the other substituent is a radical R a , an acyl group —COR a , or a functional group —COOR a , SO 2 R a or —N(R a ,R b ), R a and R b , which are identical or different, being an optionally substituted linear or branched C1-12 alkyl radical, an optionally substituted aryl group containing one or more aromatic rings, comprising 5 to 8 C, or aralkyl, wherein the alkyl substituent of said aralkyl is an optionally substituted linear or branched C1-C12 alkyl radical and the aryl group of said aralkyl is an optionally substituted aryl group containing one or more aromatic rings, comprising 5 to 8 C, or R 1 and R 2 are the same, said method comprising isoxazole derivative of formula II in which R 3 represents a hydrogen atom or R a , and R 4 is an optionally substituted linear or branched C1-C12 alkyl radical, an optionally substituted aryl group containing one or more aromatic rings, comprising 5 to 8 C, or aralkyl, wherein the alkyl substituent of said aralkyl is an optionally substituted linear or branched C1-C12 alkyl radical and the aryl group of said aralkyl is an optionally substituted aryl group containing one or more aromatic rings, comprising 5 to 8 C, to produce the diastereoisomers and enantiomers of 4-hydroxyisoleucine and derivatives thereof of general formula I or to at least one lactone of structure III in racemic form(s), or an enantiomerically enriched mixture, followed by the opening, under basic conditions, in a protic or aprotic solvent, of the required lactone or lactones and, optionally, the separation of the required form.