1: 80.4 percent / hydrazine hydrate / ethanol / Ambient temperature 2: 1.) HCl/dioxane, isoamyl nitrite / 1.) DMF, -10 deg C, 10 min, 2.) DMF, overnight 3: H2, AcOH / Pd / methanol / 12 h View Scheme

syn-benzaldehyde oxime; triethylamine; DL-threo-1,4-dimercapto-2,3-butanediol in toluene T=35°C; immobilized papain;

benzotriazol-1-ol; dicyclohexyl-carbodiimide in N,N-dimethyl-formamide T=-10°C;

bis(4-nitrophenyl) phenylphosphonate in N,N-dimethyl-formamide 1.) 0 deg C, 14 h, 2.) r.t., 5 h;