Methyl (4R,5S)-2,2,5-trimethyl-1,3-dioxolane-4-carboxylate 2,3-O-Isopropylidene-D-ribonic gamma-lactone 2,3-O-Isopropylidene-D-erythronolactone 5-Bromo-5-deoxy-2,3-O-isopropylidene-D-ribonolactone (4R,5R)-4,5-Diethoxycarbonyl-2,2-dimethyl dioxolane 5-O-(tert-Butyldimethylsilyl)-2,3-O-isopropylidene-D-ribonic acid gamma-lactone