Synthesis of b,b-branched b-amino ester derivatives through spiroaziridination of (a-trimethylsilanylmethyl)cyclohexylidene esters.

The reaction of (a-trimethylsilylmethyl)cyclohexylidene esters I (R1 = H, Me, Me3C, Ph; R2 = H, Me) with NsONHCO2Et (Ns = 4-nitrophenylsulfonyl) and CaO produces the N-(ethoxycarbonyl)spiroaziridines which, after ring-opening, gives the corresponding b,b-disubstituted b-amino esters II. The stereochem. outcome of the reaction is influenced by substituents on the cyclohexyl group.