N,O HIGHLY REGIOSELECTIVE AND STEREOSELECTIVE ALKYLATION OF NUCLEOPHILIC GLYCINE EQUIVALENTS WITH CARBONATES OF ALLYLIC ALPHA-HYDROXYPHOSPHONATES - A CONVENIENT ROUTE TO RACEMIC 2-AMINO-5-PHOSPHONO-4-PENTENOICACIDS

Palladium(0)-catalyzed allylic alkylation of diethyl (acetylamino)malo nate (6), ethyl (diphenylmethyleneamino)acetate (7), and (diphenylmeth yleneamino)acetonitrile (8), respectively, with the acrolein-derived 1 -dialkoxyphosphinyl-substituted carbonates 5 provides the gamma-substi tuted vinylphosphonates 9-11 in very good yields and with high regiose lectivity. The stereochemical outcome is dependent on the mode of nucl eophilic activation of the glycine equivalents 6-8: When the reactions are performed in the presence of N,O-bis(trimethylsilyl)acetamide (BS A) the (Z) isomers (Z)-9-(Z)-11 are highly favoured, while in the abse nce of any additional activation of the nucleophiles the corresponding (E) isomers predominate. In the latter case, upon alkylation of the S chiff base derivatives 7 and 8, up to 30% of the alpha-substitution pr oducts 12 and 13, respectively, are isolated as by-products. The vinyl phosphonates 9-11 are easily converted to the racemic 2-amino-5-phosph ono-4-pentenoic acids (Z)-3 and (E)-3, and to the saturated analogue 1 .