Lithium bromide induced ring-contraction of benzyl 2, 3-and 3, 4-anhydro-p-~(and L)- ribopyranoside (1 and 4) in HMPA/toluene or tetramethylurea (TMU)/toluene gave (R)(and S)-2-(benzyloxy)-2, 5-dihydrofuran-4-carboxaldehyde (2 and 5) together with a small amount of benzyl 4-bromo-4-deoxy-P-~(and D)-lyxopyranoside (3 and 6). The latter compound was formed with lithium bromide in l, l, l-trichloroethane. Benzyl 2, 3-and 3, 4- ...
