Synthesis of orthogonally protected D-olivoside, 1,3-di-O-acetyl-4-O-benzyl-2,6-dideoxy-D-arabinopyranose, as a C-glycosyl donor

1,3-Di-O-acetyl-4-O-benzyl-2,6-dideoxy-D-arabinopyranose (11) was synthesised from thiophenyl alpha-D-mannopyranoside (21) in an eight-step sequence. Tosylation of 21 and subsequent reaction with 2,2-dimethoxypropane gave tosylate 22, which upon treatment with lithium aluminium hydride furnished 6-deoxy glycoside 24 and by-product thiophenyl 6-deoxy-2-O-isopropyl-alpha-D-arabinopyranoside. The X-ray crystal structure of the latter was determined. Benzylation of the 4-hydroxyl group of 24 and Subsequent protecting group manipulation gave D-rhamnosyl bromide 29, which on treatment with zinc-copper couple gave the orthogonally protected D-rhamnal 30. Triphenylphosphine hydrogen bromide catalysed addition of acetic acid to 30 furnished the target molecule 11. The scandium(III) triflate promoted reaction of 11 and 2-naphthol gave the corresponding C-glycoside 36 in 86% yield. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.