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Hoffmann's synthesis of a masked cyclopropane analog of the northern hemisphere of disorazole A1. Reagents and conditions: (a) Et2Zn, CH2I2, dioxaborolane 105, CH2Cl2, 0 °C, 81%; (b) Dess–Martin periodinane, NaHCO3, CH2Cl2, 88%; (c) CrCl2, CHI3, THF, 0 °C, 49%; (d) 90, PdCl2(PPh3)2, CuI, Et3N, DMF, 49%; (e) DDQ, CH2Cl2/H2O; (f) Dess–Martin periodinane, NaHCO3, 72% (over 2 steps); (g) 98, PPh3, Hünig's base, 90 °C, then 103, LiHMDS, HMPA, THF, −78 °C to rt, 40%.
