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. Author manuscript; available in PMC: 2009 Dec 3.
Published in final edited form as: J Am Chem Soc. 2008 Dec 3;130(48):16190–16192. doi: 10.1021/ja807127s

Scheme 3. Completion of the Spiroketal Fragmenta.

Scheme 3

aConditions: (a) n-BuLi, THF, 90%, 1.5:1 syn:anti (b) for syn: DEAD, PhCOOH, PPh3, toluene, 92%, for anti: BzCl, pyridine, 95% (c) HCl, H2O, THF (d) 10 mol % AuCl, PPTS, THF, 63% (e) MeI, NaHCO3, CH3CN, H2O, 80% (f) 10 mol% Pd(OAc)2, ZnEt2, PPh3, THF, 7, 90%, 3.8:1 d.r. (g) TBSOTf, 2,6-lutidine, CH2Cl2 (h) K2CO3, MeOH (i) Bu3SnH, 5 mol% PdCl2(PPh3)2, THF, then I2, 90% over 3 steps.