Minimally competent lewis acid catalysts: Indium(III) and bismuth(III) salts produce rhamnosides (=6-deoxymannosides) in high yield and purity

Clifford Coss, Tucker Carrocci, Raina M. Maier, Jeanne E. Pemberton, Robin Polt

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Glycosylation of decan-1-ol (2), (±)-decan-2-ol (3), and (±)-methyl 3-hydroxydecanoate (4) with L-rhamnose peracetate 5 to produce rhamnosides (=6-deoxymannosides) 6, 7, and 8 in the presence of Lewis acids BF3×Et2O, Sc(OTf)3, InBr3, and Bi(OTf)3 was studied (Table1). While the strong Lewis acids BF 3×Et2O and Sc(OTf)3 were effective as glycosylation promoters, they had to be used in excess; however, glycosylation required careful control of reaction times and temperatures, and these Lewis acids produced impurities in addition to the desired glycosides. Enantiomerically pure rhamnosides (R)-1 and (S)-1 (Fig.) were obtained from L-rhamnose peracetate 5 and (±)-benzyl 3-hydroxydecanoate (9) via the diastereoisomeric rhamnosides 10 (Table2; Scheme3). The much weaker Lewis acids InBr3 and Bi(OTfl)3 produced purer products in high yield under a wider range of conditions (higher temperatures), and were effective glycosylation promoters even when used catalytically (<10% catalyst; Table2). We refer to these Lewis acids as 'minimally competent Lewis acids' (cf. Scheme4).

Original languageEnglish (US)
Pages (from-to)2652-2659
Number of pages8
JournalHelvetica Chimica Acta
Volume95
Issue number12
DOIs
StatePublished - Dec 1 2012

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Keywords

  • Catalysis
  • Glycolipids
  • Glycosides
  • Glycosylation
  • Lewis acids
  • Rhamnolipids

ASJC Scopus subject areas

  • Catalysis
  • Biochemistry
  • Drug Discovery
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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