Scheme 2.

Completion of bryostatin 9^a

^aReagents and Conditions: (a) 2,4,6-trichlorobenzoyl chloride, Et₃N, PhCH₃, then alcohol 5, DMAP, 82%; (b) PPTS (20 mol %), MeOH, [17] = 0.02 M, rt, 22 h, 65%; (c) O₃, CH₂Cl₂, −78 °C, then thiourea, 1:1 CH₂Cl₂:MeOH, rt, 72%; (d) 19, NaHMDS, THF, −78 °C → 4 °C, 79:21 Z:E, 82%; (e) HF·py, THF, rt; (f) PPTS, 20% H₂O in THF, rt, 76% combined yield, 80:20 Z:E, 52% isolated bryostatin 9.