The infrared study of the solvent effect on d-glycero-pent-2-enopyranosides (α and β) that can be used as substrate precursors in the synthesis of antibiotic ristomycin components, is reported. The higher energy content in α anomers justifies differences in intra- and interbonding with respect to β anomers of the OH and the CO moieties. This behaviour is confirmed by the analysis of half band width values in different solvent mixtures. The pronounced γC(2)–H band found only in α derivatives, makes this vibrational mode of a diagnostic importance in the assignment of the configuration.