Scheme 1. Synthesis of caspase inhibitors.
a) Ph3P=CHCO2CH2CH3, MeOH, 0°C. b) Benzylamine, −50°C, 48 h. c) H2, Pd/C, EtOH. d) Z-Lys(Boc) N-hydroxysuccinimide, CH2Cl2, 12 h. e) H2, Pd/C, EtOH. f) Z-Glu(OtBu) N-hydroxysuccinimide, CH2Cl2, 12 h. g) Montmorillonite, EtOH/H2O (5:1), 75°C, 3 h. h) 2,6-dimethylbenzoylchloride, pyridine, DMAP, DMPU, 48 h. i) Dess-Martin periodate, 0°C to rt., 4 h. j) 95% TFA/H2O, 12 h. k) labelling reagent, water, 12 h.