Ring closing metathesis (RCM) approach to the synthesis of conduramine B-2, ent-conduramine F-2, aminocyclopentitol and trihydroxyazepane

Org Biomol Chem. 2019 Jun 18;17(24):5951-5961. doi: 10.1039/c9ob01010f.

Abstract

The syntheses of conduramine B-2, ent-conduramine F-2, aminocyclopentitol and trihydroxyazepane were accomplished from a common precursor, through a divergent approach using ring closing metathesis (RCM) as the key step. Tri-O-benzyl-d-glucal was converted to 3,4,6-tri-O-benzyl-1,2-dideoxy-2-iodo-1-p-toluenesulfonamido-α-d-mannose. Exposure to NaBH4 in MeOH resulted in a facile 1,2-transposition of the -NHTs group with concomitant glycosylation to give methyl 3,4,6-tri-O-benzyl-2-deoxy-2-p-toluenesulfonamido-β-d-glucoside, which was converted into methyl 6-deoxy-6-iodo-glucoside in three steps. Zinc-mediated Vasella's rearrangement proceeded smoothly to give the pluripotent formyl-olefin, possessing both electrophilic and nucleophilic sites, which was used as a common precursor in our diversity-oriented approach. Vinylation of the carbonyl group followed by RCM and subsequent deprotection resulted in the successful synthesis of conduramine B-2 and ent-conduramine F-2 for the first time. On the other hand, the Wittig reaction of the formyl-olefin affords the diene that undergoes Grubbs' I catalyzed RCM and deprotection/reduction to provide 3-amino-cyclopentan-1,2-diol. Utilizing the nucleophilic site at the nitrogen of the common precursor, base mediated N-allylation was carried out to obtain the corresponding diene that underwent a smooth RCM to afford trihydroxyazepane.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Azepines / chemical synthesis*
  • Azepines / chemistry
  • Cyclohexanols / chemical synthesis*
  • Cyclohexanols / chemistry
  • Cyclohexylamines / chemical synthesis*
  • Cyclohexylamines / chemistry
  • Cyclopentanes / chemical synthesis*
  • Cyclopentanes / chemistry
  • Glycosylation
  • Molecular Structure

Substances

  • Azepines
  • Cyclohexanols
  • Cyclohexylamines
  • Cyclopentanes
  • conduramine B-2
  • ent-conduramine F-2