Synthesis and conformational study of chiral oxepines: the Baylis-Hillman reaction and RCM approach with sugar aldehyde

Jadhav, Vrushali H. ; Bande, Omprakash P. ; Pinjari, Rahul V. ; Gejji, Shridhar P. ; Puranik, Vedavati G. ; Dhavale, Dilip D. (2009) Synthesis and conformational study of chiral oxepines: the Baylis-Hillman reaction and RCM approach with sugar aldehyde Journal of Organic Chemistry, 74 (17). pp. 6486-6494. ISSN 0022-3263

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jo900660q

Related URL: http://dx.doi.org/10.1021/jo900660q

Abstract

The Baylis-Hillman reaction of 3-O-allyl-α-D-xylo-pentodialdo-1,4-furanose 3 afforded a diastereomeric mixture of d-gluco- and l-ido-configured a-methylene-ß-hydroxy esters 4a and 4b, respectively, in a ratio of 2:3. Reduction of the ester functionality in 4a/4b gave alcohols 5a/5b. The diene thus formed in 5a/5b was subjected to ring-closing metathesis (Grubbs' second-generation catalyst) to afford oxa-bicyclic ring system 6a/6b in high yield. Further manipulation of the acetonide functionality in 6a and 6b afforded new polyhydroxylated oxepines 1a/2a and 1b/2b, respectively. The 1H NMR of oxepines 1a and 1b in D2O showed doubling of signals indicating their existence in two different rotamers/conformers. This fact was substantiated by calculating energetics of 1 and 2 conformers using the density functional theory and correlating the calculated 1H NMR chemical shift pattern with that of the experimental spectra.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:75330
Deposited On:22 Dec 2011 13:13
Last Modified:22 Dec 2011 13:13

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