General strategy for the synthesis of unsaturated carbasugars via a diastereoselective seleno-Michael/aldol reaction

Abstract

Carbasugars are a diverse group of carbohydrate mimetics in which the ring oxygen is replaced by a methylene group. We have developed a simple and efficient carbasugar synthesis from D-aldopentoses via temporary protection of the hydroxyl moieties with TMS groups followed by consecutive intramolecular tandem Michael/aldol cyclisation. It is important to note that only the n-butylselenolate nucleophile is compatible with per-O-TMS-protected substrates. The desired products were obtained in five steps, with total yields reaching up to 40% with excellent diastereoselectivity of up to 19 : 1.