MacDonald-Fischer degradation dithioacetals

This reaction was first reported by MacDonald and Fischer in 1952. It is the degradation of hexoses into pentoses involving the steps of formation of dithioacetal, oxidation to unsaturated disulfone by means of perphthalic acid, hydrazine treatment, and benzalde-hyde splitting of the corresponding hydrazone. Therefore, the whole process is known as the MacDonald-Fischer degradation. In addition, when the unsaturated disulfone is dissolved in aqueous ammonia or methanol saturated with ammonia, 2-deoxy-2-amino sugar is resolved. This reaction in combination with mass spectroscopy was used to study the structure and stereochemistry of carbohydrates. ... 

Finally MacDonald and Fischer have prepared the free ajyZo-pento-dialdose (8) by the sulfone-degradation method. The diethyl dithioacetal of scyllo-inosose (12) was oxidized to the corresponding disulfone which, on treatment with ammonia, gave the dialdose (8). The structure was proved by converting the compound into the bis(ethylene dithioacetal) derivative, which was identical with that obtained from a /io-pentodialdose prepared by a previous method. ... 

When the paromobiosamine fraction is W-benzoylated and then hydrolyzed with dilute acid, D-ribose is one of the products. More-vigorous hydrolysis destroys the D-ribose but yields a diaminodideoxyhexose which was called paromose. A study of the products of periodate oxidation of paromose, of its di-W-acetyl derivative, and of the borohydride reduction product of the latter, revealed that paromose is a 2,6-diamino-2,6-di-deoxyhexose. In a preliminary report, Haskell and Hanessian have presented degradative evidence which establishes the stereochemical structure of paromose as that of 2,6-diamino-2,6-dideoxy-L-idose (7). Their ingenious application of the degradation described by MacDonald and Fischer and by Hough and coworkers of the 1, l-bis(ethanesulfonyl) derivatives of aldoses enabled Haskell and Hanessian to obtain, from iV,fV -diacetylparomose diethyl dithioacetal, a product which they identi-... 

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