New syntheses of L-ascorbic acid (vitamin C)

Abstract

Two new syntheses of L-ascorbic acid (1) are described, the first involving the selective oxidation of 3,5-O-benzylidene-L-gulono-1,4-lactone (4a) to 3,5-O-benzylidene-L-xylo-hexulosono-1,4-lactone hydrate (4b) and hydrolysis of (4b) to (1), and the second involving the regiospecific conversion of L-gulono-1,4-lactone (3) into ethyl 3,5 : 4,6-O-dibenzylidene-L-gulonate (5) followed by oxidative and hydrolytic conversion of (5) into ethyl L-xylo-hexulosonate (6a), a known precursor of L-ascorbic acid (1).