Consequences of the preeminent reactivity of 2-OH in sucrose: Cyclic acetalation at 2-OH and 3-OH under basic conditions

The reaction of unprotected sucrose with tert-butyl chloromethyl ketone in dimethylformamide was investigated as a model for the study of the relative reactivity of the various hydroxy groups of sucrose. Besides the monoether s arising from the substitution of the chlorine atom by 2-OH and 1'-OH of s ucrose, the major product is a tert-butyl hydroxymethyl 5-membered ring ace tal involving 2-OH and 3-OH. The formation of this product illustrates the preeminent reactivity of 2-OH towards the carbonyl group of the alpha-chlor omethyl ketone, leading to an intermediate hemiacetalic anion, which can en ter by intramolecular acetal formation through an intermediate epoxide.