Patent ID: 7884240

Claim:
A method for producing L-methionine, D-methionine or a mixture of L- and D-methionine starting from homoserine, comprising converting L-homoserine, D-homoserine or mixtures of L- and D-homoserine of the formula I: to methionine by chemical transformation, without passing through any of the intermediates N-carbamoylhomoserine, 4-(2-bromoethyl)hydantoin and 4-(2-methyl-thioethyl) hydantoin; wherein the chemical transformation of L- and/or D-homoserine is carried out in a manner that comprises: a) as a first step, performing an acid-catalyzed cyclization of said L-homoserine, D-homoserine or mixture of L- and D-homoserine, to produce a 2-amino-4-butyrolactone of formula III or salt thereof of formula IV: where X is Cl, Br, I, HSO 4 , (SO 4 ) 1/2 , H 2 PO 4 , (HPO 4 ) 1/2 , (PO 4 ) 1/3 or R′—SO 3 (where R′=methyl, ethyl, phenyl, tosyl); and b) reacting, in the presence of a Lewis acid catalyst or a Brönstedt acid catalyst, said compound of formula III or IV with methylmercaptan (MeSH) to produce L-methionine, D-methionine or a mixture of L- and D-methionine.