A simple approach to the synthesis of muramic acid and isomuramic acid: 1H and 13C NMR characterisation

A simple and efficient synthesis of 2-amino-3-O-[(R)-1-carboxyethyl]-2-deoxy-d-glucose (muramic acid, 6) and its stereoisomer 2-amino-3-O-[(S)-1-carboxyethyl]-2-deoxy-d-glucose (isomuramic acid, 7) from methyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-d-glucopyranoside (1) is described. Condensation of the O-3 oxyanion of 1 with an excess of methyl (R,S)-2-bromopropionate, followed by alkaline hydrolysis of the crude product and subsequent acidification, afforded crystalline methyl 2-acetamido-4,6-O-benzylidene-3-O-[(R,S)-1-carboxyethyl]-2-deoxy-α-d-glucopyranoside (2), in 72% yield, as a mixture of diastereomers. Esterification of 2 with an excess of diazomethane afforded quantitatively the corresponding mixture of epimeric esters, which were very easily separated by column chromatography on silica gel, giving pure (R) and (S) epimeric esters. Removal of the benzylidene and acetyl groups by acid hydrolysis gave, respectively, muramic acid (6), in 95% yield and isomuramic acid (7), in 93% yield. 1H and 13C NMR data are given. © 1997 Elsevier Science Ltd.