Iminosugars, Isoiminosugars, and Carbasugars from Activated Carbohydrate Lactones: Efficient Synthesis of Biologically Important Compounds

摘要

The synthetic potential of selectively activated aldonolactones as building blocks for synthesis of optically pure, highly func-tionalised organic molecules is highlighted. Preparation of iminosugars from selectively brominated lactones requires only two transformations, in which the ring closure by reaction with ammonia is the key step. Stereoselective alkylation of unprotected bromodeoxylactones offers a general synthetic approach to isoiminosugars. Radical induced carbocyclisation of ω-bromo-α,β-unsaturated aldonolactones yields functionalised cyclopentane /cyclohexane lactones stereospecifically, generating one or two chiral centers in the ring closing step. Stereo- and regio-selective functional group interconvertion within the bicyclic cyclopentane-lactone system gives access to hydroxy/amino substituted cyclo-pentanes. Aldonolactones provide thus in few steps access to compounds of biologically importance in an optically pure state.