N-Methyl amino acids prepn

Prepn. of optically active N-methyl amino acids of formula MeNH-CHR-COOH (I) (where R is H or an opt. OH-substd. alkyl, aryl or aralkyl gp) comprises (a) reacting the corresp optically active N-carbobenzoxy amino acid of formula Cbo-NH-CHR-COOH (II) (where Cbo = carbobenzoxy) with paraformaldehyde (III), and (b) catalytically hydrogenating the resulting 3-Cbo-5-oxazolidinone of formula (IV):Cpds. (I) are useful as antibiotic intermediates. The process gives high yields e.g. 55-90% in step (a) and 95% in step (b). The products have high optical purity. In an example, N-methyl-L-valine. HCl is prepd. from 3-Cbo-L-valine via 3-Cbo-4-isopropyl-5-oxazolidinone.