Pyranose–furanose equilibria. Studies on the methylation of 2,3-O-isopropylidene-L-rhamnose

Abstract

Methylation of 2,3-O-isopropylidene-L-rhamnose with silver oxide and methyl iodide (Purdie's reagent) yields a mixture of methyl 2,3-O-isopropylidene-4-O-methyl-α- and β-L-rhamnopyranosides and methyl 2,3-O-isopropyridene-5-O-methyl-α- and β-L-rhamnofuranosides; previously the furanoside structure had been assigned to this product. Methylation in dimethylformamide (Kuhn procedure) gives the α-furanoside and α-pyranoside derivatives only. The relationship between reactant and product composition is considered.