Synthesis of methyl 2-O-allyl-(and 3-O-allyl-) 5-O-benzyl-β-d-ribofuranoside

d-Ribose was converted into methyl 5-O-benzyl-β-d-ribofuranoside and this, on tin-mediated allylation, gave a mixture of the 2-O-allyl and 3-O-allyl derivatives which were separated by chromatography. The more polar isomer was characterised as the 3-O-allyl derivative after conversion via 3-O-allyl-5-O-benzyl-1,2-O-isopropylidene-α-d-ribofuranose (which was also synthesised from 3-O-allyl-1,2:5,6-di-O-isopropylidene-α-d-allofuranose) into the known 5-O-benzyl-1,2-O-isopropylidene-α-d-ribofuranose. Methyl 3-O-allyl-5-O-benzyl-β-d-ribofuranoside was converted into methyl 2-O-allyl-5-O-benzyl-β-d-ribofuranoside via methyl 2-O-allyl-5-O-benzyl-3-O-(prop-1-enyl)-β-d-ribofuranoside.