Aldoses dithioacetals

This article is limited to the reactions involving cyclic acetals of aldoses and aldosides. However, for comprehensiveness, or for their potential usefulness in carbohydrate chemistry, some properties of cyclic acetals not directly relevant to aldoses and aldosides are included. It may be recalled that the chemistry of dithioacetals had already been reviewed in this Series.7... 

H. Zinner, G. Rembarz, and H. Klocking, Isopropyliden-verbindungen der D-arabinose-mercaptale, Chem. Ber. 90 2688 (1957) P. A. J. Gorin, Acetonation of aldose diethyl dithio-acetals. Can. J. Chem. 43 21X18 (1965) D. G. Lance and J. K. N. Jones, Acetonation of D-xylose diethyl dithioacetal, Can. J. Chem. 45 1533 (1967). 

Dialkyl dithioacetals of fine aldoses are precursors far a useful chain-descent sc-... 

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]... 

Aldose dithioacetals, which are devoid of leaving groups, notably oxygen-bonded functions at C-2, on treatment with strong bases, afford stable C-l carbanions that allow the formation of cyclohexane derivatives when suitable leaving groups are present at C-6. 

The nuclear magnetic resonance (n.m.r.) spectra of aldose dithioacetals dissolved in pyridine-d5 or dimethyl sulfoxide-d6 generally exhibit extensively overlapping multiplets under which most of the sugar-proton resonances lie. Peracetylation of the dithioacetal, how-... 

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