A valine-derived lithiated 3-methylthiomethyl-1,3-oxazolidin-2-one for enantioselective nucleophilic hydroxymethylation, formylation, and alkoxycarbonylation of aldehydes

The 3-methylthiomethyl-4-isopropyl-5,5-diphenyl-1,3-oxazolidin-2-one (I, prepared in three steps from Boc-valine ester) is lithiated and added to aldehydes, with protecting in situ trapping of the primary adducts, to give the N,S-acetal derivatives II of 2-hydroxy aldehydes in high yields and diastereoselectivities. Cleavage (with ready recovery of the oxazolidinone auxiliary) is possible, to afford, for instance, enantiopure 1,2-diols, selectively protected (OBn, OMOM, OTBS) in the 2-position.