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. Author manuscript; available in PMC: 2014 Jun 26.
Published in final edited form as: J Am Chem Soc. 2013 Jun 14;135(25):9334–9337. doi: 10.1021/ja404401f

Scheme 2. Synthesis of pseudo-Cs symmetric intermediate.

Scheme 2

Reagents and conditions: a) PMBCl, NaH, DMF, TBAB, 0 °C, 99%; b) ClCO2Me, n-BuLi, THF, −78 to 0 °C, 99%; c) PPh3, PhOH, benzene, 50 °C, 90%; d) AD-mix-α* = K3Fe(CN)6 (3 equiv), K2CO3 (3 equiv), MeSO2NH2 (1 equiv), (DHQ)2PHAL (2 mol %), OsO4 (1 mol %), t-BuOH/H2O, 0 °C, 85%; e) triphosgene, pyridine, DMAP, CH2Cl2, −78 °C, 89%; f) PdPPh3 = Pd2(dba)3•CHCl3/PPh3 (0.3 mol %), Et3N, HCO2H, THF, reflux, 95%; g) PhCHO, KOt-Bu, THF, 0 °C, 67%; h) DIBALH, CH2Cl2, −78 °C, 95%; i) (S,S)-Leighton, Sc(OTf)3 (2.5 mol %), CH2Cl2, −10 °C, 72%, dr = 8.7:1.0; j) ethyl acrylate, Grubbs II (1.5 mol %), CH2Cl2, 99%; k) PhCHO, KOt-Bu, THF, 0 °C, 77%.