Unreacted D-mannitol (1) also present is readily removed as it is insoluble in methanol containing a little ethyl acetate, and addition of more ethyl acetate leads to crystallization of the monoacetal3. The net yield of 3 is significantly augmented by treating the mother liquors (containing a major proportion of diacetal 2) in ethyl acetate suspension with a trace of p- toluenesulfonic acid; this procedure converts 2 into the monoacetal3 and allows isolation ...
