trans-1,3-Dithiane-1,3-dioxide, a new chiral acyl anion equivalent for the preparation of masked activated acids: application to the synthesis of α-hydroxy acid derivatives

trans-1,3-Dithiane-1,3-dioxide reacts with high diastereoselectivity with aromatic aldehydes and the 1,3-dithiane-1,3-dioxide moiety can be easily converted to a thiolester without racemisation by carrying out a Pummerer reaction; the thiolester is a group that can be readily transformed into acids, esters, amides, ketones and aldehydes.