Thio-sugars. Part 1. 4-Thiotetrose derivatives via Pummerer rearrangement

Abstract

A number of 4-thiotetrose derivatives have been prepared by Pummerer rearrangement of esters of thiolan-3,4-diol 1-oxides. This synthesis illustrates the key step in a general scheme for the elaboration of glycosides and nucleosides containing sulphur in the sugar ring. In using non-sugar starting materials, it differs from other methods of obtaining these compounds. Several esters have been studied, and the protecting and directing properties of the phenylboronate function were found especially useful. The stereochemistry of the Pummerer rearrangement products is discussed, and the bicyclic phenylboronate and carbonate systems are compared. Many of the reactions are of great preparative value. The S-oxidation and rearrangement steps can be repeated, giving symmetrical bicyclic derivatives of tartaraldehyde. (Diacetoxyiodo)benzene or t-butyl perbenzoate converts esters of thiolan-3,4-diol directly into α-acyloxy-compounds, but in poor yield.