Stereoselective entry into the D-GalNAc series starting from the D-Gal one: a new access to N-acetyl-D-galactosamine and derivatives thereof

Carbohydr Res. 2009 Feb 17;344(3):298-303. doi: 10.1016/j.carres.2008.11.018. Epub 2008 Dec 10.

Abstract

A new stereoselective preparation of N-aceyl-D-galactosamine (1b) starting from the known p-methoxyphenyl 3,4-O-isopropylidene-6-O-(1-methoxy-1-methylethyl)-beta-D-galactopyranoside (10) is described using a simple strategy based on (a) epimerization at C-2 of 10 via oxidation-reduction to give the talo derivative 11, (b) amination with configurational inversion at C-2 of 11 via a S(N)2-type reaction on its 2-imidazylate, (c) anomeric deprotection of the p-methoxyphenyl beta-D-galactosamine glycoside 14, (d) complete deprotection. Applying the same protocol to 2,3:5,6:3',4'-tri-O-isopropylidene-6'-O-(1-methoxy-1-methylethyl)-lactose dimethyl acetal (4), directly obtained through acetonation of lactose, the disaccharide beta-D-GalNAcp-(1-->4)-D-Glcp (1a) was obtained with complete stereoselectivity in good (40%) overall yield from lactose.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylgalactosamine / chemical synthesis*
  • Acetylgalactosamine / chemistry
  • Acetylglucosamine / chemistry*
  • Amination
  • Carbohydrate Sequence
  • Galactose / chemistry*
  • Galactosides / chemistry*
  • Molecular Sequence Data
  • Stereoisomerism

Substances

  • 4-methoxyphenyl 3,4-O-isopropylidene-6-O-(1-methoxy-1-methylethyl)galactopyranoside
  • Galactosides
  • Acetylgalactosamine
  • Acetylglucosamine
  • Galactose