ADDITION OF 2-LITHIOFURAN TO CHIRAL ALPHA-ALKOXY NITRONES - A STEREOSELECTIVE APPROACH TO ALPHA-EPIMERIC BETA-ALKOXY-ALPHA-AMINO ACIDS

The addition of 2-lithiofuran (1) to the N-benzyl nitrones 2a-d, deriv ed from chiral alpha-alkoxy aldehydes, affords beta-alkoxy-alpha-hydro xyamino-2-alkylfurans in good yields and with syn selectivity. Convers ely, the reaction with the same nitrones precomplexed with diethylalum inum chloride leads to the same adducts but with anti selectivity. Thr ee pairs of epimeric hydroxylamines are subjected to reductive N-dehyd roxylation with titanium(III) chloride and then to furyl-carboxylic ac id conversion with ruthenium tetroxide to give the corresponding alpha -epimeric beta-alkoxy-alpha-amino acids.