Acetimidates

Acetimidates are a class of organic compounds derived from imidic acids in which the imidate nitrogen is substituted with an acetyl group. They are commonly encountered in carbohydrate chemistry as glycosyl acetimidates, where the acetimidate moiety serves as a leaving group that can be activated to promote glycosidic bond formation. In general, acetimidates are the esters of acetimidic acid, with various alkoxy or aryl substituents on the imidate oxygen.

Preparation of acetimidates is typically achieved by condensation of a hemiacetal or glycosyl hemiacetal with N-acetylimidazole or related acetylated imidate reagents, often under mild acidic conditions. Alternative routes include acetylation of preformed imidate esters or the reaction of alcohols with activated acetimidoyl sources. The exact procedure depends on the desired substituents and the substrate, but the common goal is to install the acetimidate leaving group on the oxygen atom adjacent to the imidate nitrogen.

Reactivity and applications: acetimidates are valued in organic and carbohydrate synthesis for their ability to act as glycosyl donors under mild activation. Activation with Lewis or Brønsted acids generates an activated imidate that can undergo nucleophilic attack to form glycosidic bonds, often with favorable stereochemical outcomes in certain systems. Beyond glycosylation, acetimidates are used as versatile intermediates in the synthesis of natural products and as protective or activation handles in multistep sequences.

See also: imidates, glycosyl donors, N-acetylimidazole.