Stereoselectivity in the epoxidation of carbohydrate-based oxepines

Shankar D. Markad, Shijing Xia, Nicole L. Snyder, Bikash Surana, Martha D. Morton, Christopher M. Hadad, Mark W. Peczuh

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

(Figure Presented) The facial selectivity in the DMDO epoxidation of carbohydrate-based oxepines derived from glucose, galactose, and mannose has been determined by product analysis and density functional theory (DFT, B3LYP/6-31+G**//B3LYP/6-31G*) calculations. Oxepines 3 and 4, derived from D-galactose and D-mannose, largely favor α- over β-epoxidation. The results reported here, along with selectivities in the DMDO-mediated epoxidation of D-xylose-based oxepine 1 and D-glucose-based oxepines 2 and 5 reported earlier, support a model in which electronic effects, guided by the stereochemistry of the oxygens on the oxepine ring, largely determine the stereoselectivity of epoxidation. Other contributing factors included conformational issues in the oxepine's transition state relative to the reactant, the asynchronicity in bond formation of the epoxide, and the overall steric bulk on the α- and β-faces of the oxepine. Considered together, these factors should generally predict facial selectivity in the DMDO-epoxidation of cyclic enol ethers.

Original languageEnglish (US)
Pages (from-to)6341-6354
Number of pages14
JournalJournal of Organic Chemistry
Volume73
Issue number16
DOIs
StatePublished - Aug 15 2008

ASJC Scopus subject areas

  • Organic Chemistry

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