Syntheses of unnatural N-substituted UDP-galactosamines as alternative substrates for N-acetylgalactosaminyl transferases

UDP-GalNAc analogues with slight modifications in the 2-acetamido group of the GalNAc moiety are prepared in order to study their role in the mechanism of the N-acetylgalactosaminyl transferase mediated glycosylation step. The analogues with N-propionyl, N-butyryl- and N-bromoacetyl-groups were synthesized, utilizing Khorana's morpholidate coupling method starting from D-galactosaminyl-l-phosphate after selective N-acylation of its amino group with the appropriate N-acyloxysuccinimides. Furthermore. in addition to UDP-galactosamine its 2-azido analogue has been efficiently prepared involving a metal catalyzed diazo transfer reaction. (C) 2002 Elsevier Science Ltd. All rights reserved.