Orthocarboxylic acid derivatives of carbohydrate

Esterification under mild conditions can be performed with 0-alkyl-N,N-dicyclohexylisoureas A new transesterification technique has been reported which uses molecular sieves to shift the equilibrium by selective absorption of the resulting alcohol A simple, one-stage process for the monodecarbalkoxyla-tion of malonic esters, by sodium cyanide, has been published . Orthocarboxylic acid derivatives of carbohydrates have been used for the stereospecific preparation of l,2-fran5-glycosides... 

Although the orthocarboxylic acids, R—C(OH)3, are unstable, many of their derivatives are known, stable compounds. The known carbohydrate orthoesters are all derived from the structure that results when two of the three hydroxyl groups of an orthoacid are involved in ester formation with two hydroxyl groups of the sugar molecule. General formula A represents those types which are of particular interest in the field of carbohydrates. The two adjacent carbon atoms of the five-membered ring constitute carbon atoms number 1 and 2 of an aldose and either 1 and 2, or 2 and 3 of a ketose. In certain instances it has been... 

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