Sequential cyclization-elimination route to carbohydrate-based oxepines

J Org Chem. 2005 Apr 15;70(8):3312-5. doi: 10.1021/jo048128c.

Abstract

A five-step preparation of carbohydrate-based oxepines from hept-1-enitols is presented. The hept-1-enitols were subjected to silyl protection and hydroboration/oxidation to give the protected heptan-1-itols. Swern oxidation of the homologated alcohols followed by sequential acetal formation/cyclization provided methyl 2-deoxyseptanosides that underwent elimination reactions to give the carbohydrate-based oxepines. The new sequence is an alternative to the ring-closing metathesis for the synthesis of carbohydrate-based oxepines from protected pyranose sugars. The product oxepines can serve as glycosyl donors in the synthesis of novel septanose carbohydrates. In addition, C-methylenealdehydo arabinofuranoside 16 was formed from 2-deoxyseptanoside 10 as the only product during protic acid mediated elimination reactions. This novel ring contraction complements other reported preparations of C-methylenaldehydo furanosides and underscores the acid-mediated reactivity introduced by competing eliminations between the C-1/C-2 and C-2/C-3 bonds.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbohydrates / chemistry*
  • Catalysis
  • Cyclization
  • Indicators and Reagents
  • Magnetic Resonance Spectroscopy
  • Molecular Structure
  • Oxepins / chemical synthesis*
  • Oxidation-Reduction

Substances

  • Carbohydrates
  • Indicators and Reagents
  • Oxepins