METHOD OF PRODUCING METHIONINE FROM HOMOSERINE Russian patent published in 2013 - IPC C07C319/14 C07C323/58 

FIELD: chemistry.

SUBSTANCE: invention relates to novel methods of producing L-methionine, D-methionine or any mixture of L- and D-methionine from homoserine and is characterised by that L-homoserine, D-homoserine or mixtures of L- and D-homoserine of formula (I) are chemically converted to methionine without formation of intermediate N-carbamoyl homoserine, 4-(2-bromoethyl)hydantoin and 4-(2-methylthioethyl)hydantoin. According to the first of the disclosed methods, chemical conversion involves a first step for ring closure in the presence of an acid catalyst to obtain the corresponding 2-amino-4-butyrolactone of formula III or salt thereof of formula IV (values of X are given in claim 1), and at the second step that lactone or salt thereof, by reacting with MeSH, is converted to L-methionine, D-methionine or a mixture of L- and D-methionine. According to the second of the disclosed methods, chemical conversion consists of steps a) to c). At step a) homoserine of formula (I) undergoes basic catalytic N-acylation with an acylating agent and ring closure to N-acyl-L- and/or D-homoserine lactone of formula (VIII) at temperature ranging from 20 to 100°C, preferably from 50 to 90°C, the acylating agent having general formula R-CO-X¹ (values of R and X¹ are given in claim 6). At step b) the N-acylhomoserine lactone obtained at step a), by reacting with MeSH in the presence of a base catalyst, is converted to the corresponding N-acylmethionine of formula (VII) At step c) the N-actylmethionine obtained at step b) is hydrolysed at temperature higher than 95°C to the corresponding methionine. The base catalyst used at step b) is a trialkylamine of general formula NR³R⁴R⁵ (values of R³, R⁴ and R⁵ are given in claim 6) or DABCO, DBU, TBD, hexamethylenetetramine, tetramethylethylenediamine or tetramethyl guanidine. Step b) uses 1-20 mole equivalents, preferably 1-10 mole equivalents, of the base with respect to the hydroxide equivalent.

EFFECT: improved method.

18 cl, 1 tbl, 10 ex