Selective Ring-opening of Cyclic Acetals with Carboxylic Acid-Trifluoroacetic Anhydride Mixtures

Selective Ring-opening of Cyclic Acetals with Carboxylic Acid-Trifluoroacetic Anhydride Mixtures 

The use of an acylating medium for effecting scission of the acetal ring of a cyclic acetal of a sugar was first demonstrated in the conversion of methyl 4,6-0-ethylidene- 3-D-glucoside into methyl 4-0-(l-acetoxyethyl)-6-0-acetyl- 3-D-glucoside. The reagent employed was a 0.1% (vol./vol.) solution of concentrated sulfuric acid in acetic anhydride at room tempera- 

The attempted henzoylation of the free hydroxyl group in (17) revealed some interesting stereochemical features (of this and similar molecules) which determine the reactivity to further attack hy different reagents. Although acetylation of the C-3-hydroxyl group with acetic anhydride in 

Studies of acid hydrolysis, acetolysis, and ease of formation of cyclic 

Tri-O-methylene-D-mannitol (1 mole), on treatment with the 10 1 mixture, that is, acetic acid (45 moles) and trifiuoroacetic anhydride (4.5 moles), showed a similar differentiation in reactivity of the acetal rings. The only product recoverable in the early stages of the reaction at 50° was (30), with the further product (31) appearing much later. Higher temperatures were 

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