A new synthesis of (+)-cyclophellitol, a potent β-glucosidase inhibitor, has been completed in nine steps from d-xylose. The key transformations involve a zinc-mediated fragmentation of benzyl-protected methyl 5-deoxy-5-iodo-xylofuranoside followed by a highly diastereoselective indium-mediated coupling with ethyl 4-bromocrotonate. Subsequent ring-closing olefin metathesis, ester reduction, olefin epoxidation
A convenient approach to the construction of dihydroxylated unsaturated azepanes featuring a functional group (ethoxycarbonyl)methyl or (cyano)methyl at C-2 was achieved from a pent-4-enal synthon obtained in four steps from D-xylose. The key step of the sequence relied on the conjugate addition of allylamine to alpha,beta-unsaturated ester or nitrile, prepared by Wadsworth-Emmons olefination. Subsequent RCM afforded the target unsaturated azepanes. (C) 2012 Elsevier Ltd. All rights reserved.