Synthesis of (R)- or (S)-diphenylphosphinoyl hydroxy aldehydes and 1,2-diols using Mukaiyama's bicyclic aminal methodology and Sharpless asymmetric dihydroxylation

Abstract

Two different approaches to diphenylphosphinoyl hydroxy aldehydes and 1,2-diols are compared. A lengthy chiral auxiliary approach using proline-derived aminals enables hydroxy aldehydes and 1,2-diols of known absolute stereochemistry and high enantiomeric excess to be synthesised. In contrast, a much shorter asymmetric dihydroxylation route generates 1,2-diols with lower enantiomeric excesses and unexpected (in view of Sharpless's mnemonic) absolute stereochemistry. The dihydroxylation results are thus of both mechanistic and synthetic value.