Nucleophilic displacement reactions in carbohydrates. Part X. The solvolysis of benzyl 5-O-p-bromophenylsulphonyl-2,3-O-isopropylidene-β-D-ribofuranoside : a benzyloxy-group migration

Abstract

Solvolysis of benzyl 5-O-p-bromophenylsulphonyl-2,3-O-isopropylidene-β-D-ribofuranoside (1) in 50% aqueous methanol-sodium acetate yielded principally benzyl 2,3-O-isopropylidene-β-D-ribofuranoside (2), benzyl 2,3-O-isopropylidene-5-O-methyl-β-D-ribofuranoside (3), 5-O-benzyl-2,3-O-isopropylidene-β-D-ribofuranose (4), and methyl 5-O-benzyl-2,3-O-isopropylidene-β-D-ribofuranoside (5). Compounds (2) and (3) arise by direct solvolytic displacement of the sulphonic ester group while the rearranged products (4) and (5) are formed as a consequence of benzyloxy-group participation in the displacement of the sulphonic ester group.