Aldos-2-uloses, preparation

Stone78 subsequently reported an improved method for preparing aldos-2-uloses from aldoses. D-Xylose was directly oxidized to D-threo-pentos-2-ulose-(in 34% yield) by cupric acetate in the presence... 

This general synthesis—the addition of cyanide to an aldos-2-ulose, followed by cyclization and hydrolysis—proved of great value in the preparation of analogs of ascorbic acid,80 but is not competitive with later syntheses of L-ascorbic acid, because an efficient and inexpensive method for the synthesis of 9 has not yet been developed. 

These compounds are formally derived from aldoses by oxidation of a secondary hydroxyl group to a ketone group. The well-known aldos-2-uloses (usually termed simply aldosuloses or osones in former usage) have long been known in the form of their bis(hydrazone) derivatives, the osazones. Deoxyaldosuloses have been implicated as intermediates in a variety of degradation reactions. Aldos-3-, -4-, and -5-uloses have been prepared, principally as intermediates for synthesis. 

The principal synthetic application of the aldos-2-uloses has been as intermediates in the preparation of L-ascorbic acids (see Section II.5.a). Aldos-2-uloses can be oxidized to 2-glyculosonic acids. They are more stable... 

Crystalline 1,2 2,3 5,6-tri-0-isopropylidene-2(2 )-o -D-araZ) o-hexofura-nos-2-ulose (237), prepared by acetonation of 205, is useful for purification of the aldosulose, as it can be hydrolyzed, regenerating 205.455 Aldos-2-ulose 1,1-dithioacetals have also been obtained crystalline.456... 

The preparation of some aldos-5-uloses, starting from hexose-5-enes was introduced by Helferich and Himmen in their synthesis of 6-deoxy-n-xylo-hexos-5-ulose. 

The oxidation of aldose phenylosazones to aldos-2-uloses (osones) and the g.l.c. separation of the TMS ethers of the products have been examined in the cases of the D-f/ reo-pentose, D-arabino-, D-lyxo-, L-xy/o-hexose compounds, and two disaccharide derivatives. A new approach to the synthesis of ketonic carbohydrate derivatives involves the treatment of amino-compounds with sterically hindered quinones to prepare imines which rearrange as shown in Scheme 1 to give products which undergo hydrolysis to ketones. The method gave the 2- and 3-ulosides, respectively, when applied to methyl 2-amino-2-deoxy-a- and 3-D-glucopyranoside and methyl 3-amino-3-deoxy-j3-D-allo-furanoside. ... 

The antibiotic cortalcerone 42, a metabolite of the fungus corticium caeruleum, has been prepared from D-glucose using a pyranose 2-oxidase and an aldos-2-ulose dehydratase to prepare the unstable tricarbonyl derivative 41 and hence the product, as shown in Scheme 1. ... 

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