Sorbose, VII

Ohle and Just112 have carried out the following sequence 1,2-isopro-pylidene-D-fructopyranose 3-p-toluenesulfonate —> l,2-isopvopylidene-3,4-anhydro-D-psicose —> l,2-isopropylidene-4-methyl-D-sorbose (VII), ([a]D -81.6°). Since the introduction of a methyl group does not alter greatly the specific rotation, it is to be expected that the parent 1,2-iso-... 

Industrial-scale production of ascorbic acid also starts with glucose. The sugar is first reduced to sorbitol (VI) and then oxidized with Acetobac-ter suboxidans to L-sorbose (VII) which after cyclization and conversion to the diisopropylidene derivative (VIII) is oxidized to the corresponding derivative of L-2-oxogulonic acid (IX). After removal of the protecting isopropylidene groups, L-ascorbic acid (vitamin C) is obtained via L-2-oxogulonic acid (X cf. Reaction 18.41). 

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