2-C-Methyl-2,3-O-isopropylidene-D-ribono-1,4-lactone is used in the synthesis of carbon-branched carbohydrate chirons: enantiomers of 2-C-Methyl-ribono-1,4-lactone and 2-C-Methyl-arabinonolactone, as Neplanocyn A intermediates, a potential anti-HCV agent.