Scheme 3. Synthesis of 6-epi-ent-cryptocaryol B (2).
Reagents and conditions: a) DDQ, CH2Cl2, H2O, 0 °C, 92%; b) Dess-Martin periodinane, CH2Cl2, 0 °C, 81%; c) 1-pentadecyne, n-BuLi, THF, −78 °C; d) Dess-Martin periodinane, CH2Cl2, 0 °C, 67 % (two steps); e) (S,S)-Noyori (5 mol %), Et3N, HCO2H, 94%; f) NBSH, Et3N, CH2Cl2, 90%; g) DIBALH, CH2Cl2, −78 °C, 87%; h) Ac2O, Et3N, DMAP, CH2Cl2, 0 °C, 72%; i) (S,S)-Leighton, Sc(OTf)3 (5 mol %), CH2Cl2, −10 °C, 75%; j) acrylic acid, DCC, DMAP, CH2Cl2, 61%; k) Grubbs I (5 mol %), CH2Cl2, reflux, 75%; l) AcOH/H2O (4:1), 80 °C, 75%.
