Oxidation of the Gulono-l,4-lactones and Derivatives

The most important oxidation product of L-gulono-1,4-lactone (I) is, without a doubt, L-ascorbic acid (6 vitamin C), and the most important oxidation product of L-gulonic acid (3) is L-xyZo-2-hexulosonic acid (5), which serves as a key intermediate in the commercial production of L-ascorbic acid. The literature covering the methods by which 1 or 3 (or derivatives thereof) has been converted into 6 or 5, as well as other methods for the preparation of 6, has been reviewed,1 and will not be discussed here. 

When 2,3-O-isopropylidene-D-gulono-1,4-lactone (52) was treated with sodium periodate, 3,4-O-isopropylidene-L-lyxurono-l,4-lactone (84) was formed26 this was converted in several steps into D-arabin-ose. Benzyl 2,4,5,6-tetra-O -benzyl-L-gulonate was oxidized to benzyl 

6- tetra-Obenzyl-L-xyZo-3-hexulosonate (85) which, on debenzyl-ation, underwent81 decarboxylation, and formation of L-threo-2-pent-ulose (86). Heyns and coworkers128 oxidized 3,6-anhydro-L-gulono-1,4-lactone (62) with air in the presence of platinum oxide, to afford 

6- anhydro-L-xt/Zo-2-hexulosono-l,4-lactone in 75% yield. On oxidation of D-gulonic acid with nitric acid and sodium metavanadate, L-threaric (dextro-tartaric) acid (13.6%), oxalic acid, and D-glucaric acid are formed.129 

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