Figure 3: The 6π-electrocyclization/aromatization approach towards the total synthesis of xiamycin A. | Nature Communications

Figure 3: The 6π-electrocyclization/aromatization approach towards the total synthesis of xiamycin A.

From: Total synthesis and antiviral activity of indolosesquiterpenoids from the xiamycin and oridamycin families

Figure 3

Reagents and conditions: (a) AZADO (5 mol%), PhI(OAc)2 (3.0 eq), CH2Cl2, 22 °C, 6 h; (b) TMSEOH (1.2 eq), EDC·HCl (1.1 eq), 4-DMAP (1.0 eq), CH2Cl2, 22 °C, 5 h, 76% (two steps); (c) Cp2TiCl2 (20 mol%), Mn (8.0 eq), iPr2NEt (6.0 eq), TMSCl (5.0 eq), THF, 22 °C, 4 h; (d) TBSCl (1.2 eq), imidazole (1.5 eq), DMF, 22 °C, 10 h; (e) K2CO3 (1.0 eq), MeOH, 22 °C, 3 h, 44% (3 steps); (f) DMP (1.5 eq), CH2Cl2, 22 °C, 30 min; (g) 15 or 18 (3.0 eq), THF, 22 °C, 40 min; (h) MsCl (1.2 eq), iPr2NEt (1.5 eq), CH2Cl2, 0 °C, 1 h, 75% for 16 (three steps), 71% for 20 (three steps); (i) air, DMSO, 120 °C, 2 h, 80% for 17, 76% for 19; (j) Mg (2.0 eq), MeOH, 22 °C, 1 h, 98%; (k) TASF (2.0 eq), DMF, 50 °C, 95%.

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