MICHAEL-TYPE ADDITION OF PHTHALIMIDE SALTS TO CHIRAL ALPHA,BETA-UNSATURATED IMIDES

The synthesis of (R)-(-)-3-aminobutanoic acid starting from chiral alp ha,beta-unsaturated imide 1b is described, by means of the nucleophili c attack of several phthalimido derivatives in the presence of a Lewis acid. The reaction was studied in some details and chloromagnesium ph thalimide afforded the better results with 95:5 diastereomeric ratio a nd 90% yield. Furthermore the resulting enolate was trapped performing the reaction in the presence of benzenesulfonyl bromide and the 2-bro mo-3-phthalimido derivative 4 was obtained in good yield and high dias tereoselectivity and successively transformed into the corresponding 2 -azido-3-phthalimido derivative 6 by displacement of the bromide with sodium azide.