D-XYLOSE DERIVED OXAZOLIDIN-2-ONES AS CHIRAL AUXILIARIES IN STEREOSELECTIVE ALDOL REACTIONS

Chiral N-acylated oxazolidin-2-one derivatives from D-xylose have been shown to undergo diastereoselective aldol reactions via their lithium imide enolates to afford beta-hydroxylated products. Aliphatic substr ates and aldehydes were shown to yield 'non-Evans' syn-aldols readily interpreted by assuming chelated chair-like transition states. When su bstrates and aldehydes bearing aromatic groups are used chelated boat- or twist-boat-like transition states seem to become similarly or even more probable so that anti- or syn-aldols are also formed from cis- o r trans-enolates, respectively. (C) 1997 Elsevier Science Ltd.