Scheme 4.
Synthesis of zygosporamide.
Reagents and conditions: (a) l-Leu-OMe*HCl, EDC, HOBt, DIPEA, CH2Cl2 (92%); (b) aq. LiOH, THF, MeOH; (c) l-Phe-OMe*HCl, EDC, HOBt, DIPEA (95%); (d) l-Phe-OBn, BOP, DIPEA, MeCN (90%); (e) TCBC (2,4,6-trichlorobenzoyl chloride, Yamaguchi reagent), DIPEA, DMAP, toluene (80%); (f) Pd/C, H2, MeOH; (g) HATU, DIPEA, DMF/CH2Cl2, (1:4), 0.002 M (50%).