Synthesis and fast-atom-bombardment-mass spectrometry of N-acetylmuramoyl-L-alanyl-D-isoglutamine (MDP).

N-Acetylmuramoyl-L-alanyl-D-isoglutamine (MDP) was synthesized by a series of condensations of appropriate reagents, followed by hydrogenolysis. Each intermediate step resulted in a stable, crystalline product. D-Isoglutamine 4-benzyl ester was condensed with N-(tert-butoxycarbonyl)-L-alanine N-hydroxysuccinimide ester, to give N-(tert-butoxycarbonyl)-L-alanyl-D-isoglutamine benzyl ester. Condensation of L-alanyl-D-isoglutamine benzyl ester with N-acetyl-1-O-benzyl-4,6-O-benzylidenemuramic acid, followed by hydrogenolysis, gave MDP. The synthetic scheme was shown to be capable of producing gram quantities of highly pure MDP, as well as a few of its analogs. The synthetic MDP was characterized by analytical and biological methods, and it was found that the use of fast-atom-bombardment-mass spectrometry may greatly simplify the characterization process.