ALKYLATION OF CHIRAL PHOSPHONOGLYCINE EQUIVALENTS - ASYMMETRIC-SYNTHESIS OF DIETHYL ALPHA-AMINO-ALPHA-ALKYL-PHOSPHONATES

A model was developed to rationalize the experimental results of the a lkylation of chiral phosphonoglycine equivalents yielding alpha-amino- alpha-alkyl-phosphonates. The model studies, carried out using semiemp irical calculations, have emphasized the role of the chelating effects in influencing the diastereoselectivity of the alkylation step. Chela tion can be optimized by tuning the functionality of the substituent a t carbon C-1 of the camphor skeleton, By employing 2d, as suggested by the modelling, a major improvement in the enantiomeric excesses of co mpounds 5 (R=CH3, C2H5) was obtained.