Synthesis of a polymer-bound galactosylamine and its application as an immobilized chiral auxiliary in stereoselective syntheses of piperidine and amino acid derivatives

Chemistry. 2004 Sep 6;10(17):4136-49. doi: 10.1002/chem.200400253.

Abstract

A 2,3,4-tri-O-pivaloylated beta-D-galactopyranosyl azide bearing a hydroxy-functionalized spacer unit at the C-6 position of the galactose was synthesized and immobilized on the solid phase by using a polymer-bound chlorosilane. The azide was reduced to the corresponding galactopyranosylamine, which served as a versatile chiral auxiliary in highly diastereoselective Ugi four-component condensation reactions at ambient temperature. Fluoride-induced cleavage from the polymeric support furnished N-glycosylated N-acylated alpha-amino acid amides. The reaction of the immobilized galactosylamine with aldehydes gave rise to the corresponding aldimines, which underwent a domino Mannich-Michael condensation reaction with Danishefsky's diene at ambient temperature to yield 2-substituted 5,6-didehydropiperidin-4-ones on the solid phase. Subsequent cleavage with tetra-n-butylammonium fluoride delivered the N-glycosylated products in high yields, purities, and diastereoselectivities. A chemoselective 1,4-hydride addition to the polymer-bound dehydropiperidinones was achieved in the presence of the bulky oxygenophilic Lewis acid methylaluminum [bis(2,6-di-tert-butyl-4-methylphenoxide)]. The conjugate addition of cyano-modified Gilman reagents to the immobilized dehydropiperidinones furnished 2,6-cis-substituted piperidine derivatives as the major diastereomers that were isolated after cleavage from the support.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / chemical synthesis*
  • Chromatography, Liquid
  • Chromatography, Thin Layer
  • Galactosamine / chemistry*
  • Indicators and Reagents
  • Magnetic Resonance Spectroscopy
  • Mass Spectrometry
  • Molecular Conformation
  • Piperidines / chemical synthesis*
  • Polymers
  • Spectrophotometry, Ultraviolet
  • Stereoisomerism

Substances

  • Amino Acids
  • Indicators and Reagents
  • Piperidines
  • Polymers
  • Galactosamine