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Total synthesis of novel antibiotics pyloricidin A, B and C and their application in the study of pyloricidin derivatives.

The novel natural antibiotics pyloricidin A, B and C, which possess potent and highly selective anti-Helicobacter pylori activity, were synthesized from D-galactosamine as a chiral template for the common (2S,3R,4R,5S)-5-amino-2,3,4,6-tetrahydroxyhexanoic acid moiety. The synthetic strategy, using 2-amino-2-deoxyuronic acid derivatives as key intermediates, was also useful to prepare a series of derivatives modified at the beta-D-phenylalanine and with altered stereochemistry on the 5-amino-2,3,4,6-tetrahydroxyhexanoic acid moiety. From the drastic decrease of their anti-H. pylori activity, it was clear that the beta-D-phenylalanine part and the stereochemistry of the 5-amino-2,3,4,6-tetrahydroxyhexanoic acid moiety were significant for the activity.