Luciana Auzzas

Advances in Chemical Synthesis of Carbasugars and Analogues

ABSTRACT Carbasugars, carbocyclic structures where a carbon atom – usually a methylene – replaces oxygen in the heterocyclic motif of the carbohydrates, represent an important class of natural and synthetic compounds that exhibit far-reaching biological effects. In this article the carbasugars have been divided into three main categories, those embodying a cyclopentane motif (furanoid carbasugars), those incorporating a cyclohexane motif (pyranoid carbasugars), and those bearing rather rare cyclopropane, cyclobutane, cycloheptane, and cyclooctane cores (contracted and expanded carbasugars). In the three major sections of this article, the most representative syntheses of the carbasugars and their closest analogues are analyzed, and the key carbocycle forming manoeuvres are focused on in particular detail. Reference to the observed biological activity is also included, where sufficient data is available. Only recent literature from the 90s onwards was considered, although the most pioneer works on this matter have also been remembered. Lack of space did not permit us to cover this field completely; however, in order to offer the reader a wider coverage of this subject matter, two tables listing important review articles and papers dealing with carbasugars, not discussed in the text, have been included in the final section of this account.

Synthesis of a Small Repertoire of Non-Racemic 5a-Carbahexopyranoses and 1-Thio-5a-carbahexopyranoses (‡)

A short and practical entry to optically pure 5a-carbahexopyranose and 1-thio-5a-carbahexopyranose representatives is described. Besides a few functional group and protecting group manipulations, the synthetic scheme counts on two fundamental carbon−carbon bond-forming reactions, namely (i) a regio- and stereoselective aldol addition between heterocyclic (silyloxy)diene donors (6 or 13) and D-glyceraldehyde as the acceptor (7) and (ii) a chemo- and stereoselective silylative cycloaldolization involving bifunctional aldehydes (10, 16, and 21). The 1H NMR based configurational and conformational assignment of target structures 1−5 and bicyclic intermediates 11, 12, 17, 18, and 22 is discussed. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

A short entry to novel C(2)-methyl branched 4a-carbafuranoses

Abstract A concise, diastereoselective synthesis of 2- C -methyl-4a-carba-β- d -lyxofuranose 13 and 2- C -methyl-4a-carba-β- d -arabinofuranose 14 , two novel representatives of the branched-chain carbasugar family, is presented. The construction is based on the sequential execution of two strategic carbon–carbon bond-forming reactions, a vinylogous crossed aldol addition ( 1 + 2 → 3 ), and a rare silylative cycloaldolization ( 8 → 9 + 10 ).