Organocatalytic Site-Selective Acylation of Carbohydrates and Polyol Compounds.

Development and scope of conventionally difficult molecular transformation on site-selective acylation of carbohydrates and polyol compounds are described. A salient feature is that the site-selectivity can be controlled independently from the intrinsic reactivity of the substrate, i.e., catalyst-controlled selectivity. Therefore, some substrates undergo acylation with reversal of their intrinsic reactivity. The mechanistic aspects of catalyst-controlled site-selective acylation are discussed with the emphasis on the strategy relying on the accelerative reaction rather than the decelerative one. An unconventional retrosynthetic route based on catalyst-controlled site-selective acylation is proposed toward extremely short-step total synthesis of natural glycosides of an ellagitannin family. Application to the late-stage functionalization of the complex natural products of biological interest is also described.