COOT R EtBr R COoT COoT EtoNa EtoNa R2 CooT H2N NH2 R NH ≥=0 R EtoNa NH R1Br: iso-Amyl BromideCOOEt COOEt NH NH O O O R1X EtONa EtBr EtONa R1 R2 COOEt R COOEt 1 R2 H2N NH2 O EtONa R1Br: iso-Amyl Bromide