Sorbose cyclic acetals

Dialkyl dithioacetal derivatives of ketoses, such as D-fiuctose and L-sorbose, me inaccessible directly from the parent sugars, the ketose undergoing extensive decomposition under the conditions employed for mercaptaladon of aldoses. Such derivatives can, however, be prepared by indirect methods. Acetylation of D-fiuctose [40] and L-soibose with acetic adiydride and zinc chloride [41] leads to good yields of acyclic pentaacetates in which foe ketose carbonyl is not involved in a cyclic acetal. Subsequent treatment of these acetylated derivatives with thiols affords foe acetylated dialkyl dithioacetals in satisfactory yields, and conventional deacetylation affords foe unprotected dialkyl dithioacetals [40,41]... 

Crystalline cyclic acetals of L-sorbose with other aldehydes or ketones have been mentioned earlier in this review, for example the 1-tosyl and 1-benzoyl esters of 3,5 4,6-diethylidene-L-sorbosew (page 111) and dicy-clohexylidene-L-sorbose 106 (page 120). 

A sirupy pentapropionate of L-sorbose was described by Hurd and Gordon.142 Crystalline esters of L-sorbose, such as the 1-benzoyl-,55 1-p-aminobenzoyl-148 and 1-tosyl-, 144,56 have also been synthesized. 1-p-Aminobenzoyl-L-sorbose was prepared as a possible substance for measuring the rate of glomerular filtration. It was synthesized by esterifying 2,3 4,6-diisopropylidene-L-sorbose with p-nitrobenzoyl chloride, with subsequent reduction of the nitrobenzoyl ester to 1-p-amino-benzoyl-2,3 4,6-diisopropylidene-L-sorbose. Removal of the isopropyli-dene groups by dilute acid hydrolysis furnished the desired product. 1-Tosyl-L-sorbose was independently prepared by two different methods. The first method,55 discussed on page 110, involves the oxidation of a properly substituted sorbitol derivative, while the latter method144 is similar to the one used for the preparation of the 1-p-aminobenzoyl derivative, namely esterification of 2,3 4,6-diisopropylidene-L-sorbose, followed by acid hydrolysis. This cyclic acetal has also been esterified to the crystalline l-mesyl-2,3 4,6-diisopropylidene-L-sorbofuranose by... 

Emil Fischer first described the condensation of D-fructose with acetone in 1895, and most of the early work on cyclic acetals of ketoses was performed with D-fructose. In 1934, Reichstein and Griissner published their classic synthesis of L-ascorbic acid (vitamin C), in which L-sorbose was converted into 2,3 4,6-di-0-isopropylidene-a-L-sorbofuranose or other di-alkylidene acetals. The emphasis of research activity then shifted to L-sorbose, and to the elucidation of an optimal procedure for preparing such diacetals. At about the same time, Levene and Tipson used isopropylidene acetals as derivatives for the purification of L-cri/thro-pentulose (as the di-isopropylidene acetal) and D-thrco-pentulose (as the monoisopropyli-dene acetal). Soon thereafter, Reichstein and coworkers used diisopropylidene acetals of D- and L-psicose, and D-tagatose, to purify the respective sugars. 

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