Abstract
Two approaches were used for the synthesis of 4-O-(α-l-rhamno-pyranosyl)-d-glucopyranuronic acid (1). Rhamnosylation of benzyl 6-O-allyl-2,3-di-O-benzyl-β-d-glucopyranoside (7), followed by deallylation, oxidation to uronic acid, and deblocking afforded 1. Alternatively, rhamnosylation of suitably protected d-glucuronic acid derivatives (25 and 26) gave the protected pseudoaldoBiouronic acid derivatives (19 and 30), which were deprotected. Rhamnosylations were performed in high stereoselectivity without neighbouring-group assistance using 2,3,4-tri-O-benzyl-1-O-trichloroacetimidoyl-α-l-rharnnopyranose (27) with tri-fluoromethanesulfonic acid catalysis.

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