01772nas a2200205   4500008004100000022001400041245012400055210006900179260007100248300001400319490000700333520095600340100002501296700002501321700002301346700002401369700002601393700002301419856012401442       2009                        eng d  a0022-326300aSynthesis and conformational study of chiral oxepines: the baylis-hillman reaction and RCM approach with sugar aldehyde0 aSynthesis and conformational study of chiral oxepines the baylis  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP  a6486-64940 v743 a<p>The Baylis-Hillman reaction of 3-O-allyl-alpha-D-xylo-pentodialdo-1,4-furanose 3 afforded a diastereomeric mixture of D-gluco- and L-ido-configured alpha-methylene-beta-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 aectonide functionality in 6a and 6b afforded new polyhydroxylated oxepines 1a/2a and 1b/2b, respectively. The (1)H NMR of oxepines 1a and 1b in D(2)O 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 (1)H NMR chemical shift pattern with that of the experimental spectra.</p>1 aJadhav, Vrushali, H.1 aBande, Omprakash, P.1 aPinjari, Rahul, V.1 aGejji, Shridhar, P.1 aPuranik, Vedavati, G.1 aDhavale, Dilip, D.  uhttps://library.ncl.res.in/content/synthesis-and-conformational-study-chiral-oxepines-baylis-hillman-reaction-and-rcm-0