Stereoselective Route to a New Class of Phosphasugars. Novel Analogues of 2-Deoxyglucose and 2-Deoyallose

Abstract

Heterosugars are inherently interesting substances because of the ubiquity of carbohydrates in living systems, but the stereochemical complexity of the pentoses and hexoses has ensured that only restricted ranges of heteroatom analogues have been made. To avoid tedious separation of a multiplicity of stereoisomers, the preferred approach has been to insert a heteroatom into an existing sugar framework. In the area of phosphasugars,1 this has meant either replacement of the hemiacetal oxygen, or of C(1), by phosphorus. Synthetic convenience dictates that the phosphorus atom frequently carries an alkyl or an aryl group, and this would be expected to detract from the isosteric nature of the resultant heterosugar. We wished to develop more general routes to phosphasugars where the phosphorus atom replaced a carbon atom and carried no other carbon substituents. Ideally, this would involve replacing CH(OH) with PH(O), but it is synthetically simpler to use P(O)OAlk since this group is convertible to PH(O).2