Reagents and conditions: a) KH; PMBCl, THF, 94%; b) CSA, MeOH/THF, 90%; c) TBSOTf, 2,6-lut, CH2Cl2; CSA, MeOH, 91%; d) Ag2O, MeI, CH3CN, 60 °C, 76%; e) TBAF, THF, 98%; f) Dess-Martin periodinane, CH2Cl2, 96%; g) MeMgBr, PhCH3, −78 °C, 75%; h) DDQ, CH2Cl2/H2O, 0 °C, 93%; i) NaH; BnBr, THF, 87%; j) CH2=CHCHO, 2nd Hoveyda-Grubbs cat., DCM, 40 °C, 83%, >10:1 E:Z; k) NaBH4, MeOH; l) D-(−)-DET, Ti(OiPr)4, TBHP, DCM, −25 °C, (64% 2 steps), 5:1 d.r.; m) I2, imid, PPh3, Et2O/CH3CN, 87%; n) CuBr DMS, CH2=CHMgBr, HMPA, THF, −25 °C, 84%; o) 2nd Hoveyda-Grubbs cat., DCM, 40 °C, 85%; p) 2nd Hoveyda-Grubbs cat., DCM, 40 °C, 74%, 2.6:1 E:Z; q) TESCl, Imid, DMF, 82%; r) 19, Oxone, Bu4NHSO4, K2CO3, pH=10.5, DMM/CH3CN, 82%, 93:7 d.r.; s) TBAF, THF, 77%. t) H2O, 60 °C, 5 d; Ac2O, Et3N; u) H2O, 80 °C, 9 d; Ac2O, Et3N.