Convergent synthesis of epoxide 9.
Reagents and conditions a) DIBAL-H, CH2Cl2, −78 °C. b) Ph2CH2, nBuLi, THF, 0 °C, 82% (2 steps). c) 1-Phenyl-1H-tetrazole-5-thiol, Ph3P, DIAD, THF, 97%. d) NaH, DMF, 0 °C, then MeI, 85%. e) m-CPBA, NaHCO3, CH2Cl2, 0 °C, 95%. f) KHMDS, DME, −78 °C, then 15, 63%. g) Bu4NF, THF, 95%. h) Shi catalyst, KHSO5, (MeO)2CH2, CH3CN, H2O, −5 °C, 94%. i) Boc2O, N-methylimidazole, PhMe, 83%.