Scheme 1: Synthesis of Z-GP-CI-994. Reagents and conditions: (a) (CH3CO)2O, 70°C, 4 hr, 92.3%; (b) Et3N/ClCOOEt, benzene-1,2-diamine, rt, 10 hr, 51.5%; (c) Et3N/ClCOOEt, Z-GP-OH, rt, 20 hr, 53.8%.