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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 2. Toward the Synthesis of the Spiroketal Fragmenta.

Scheme 2

aConditions: (a) 0.1 mol% (R)-BINAP, 0.05 mol% [RuCl2(C6H6)]2, MeOH, H2 1800 psi, 92%, 99% ee (b) PMBO(C=NH)CCl3, 1 mol% Cu(OTf)2, toluene, 85% (c) DIBAL-H, CH2Cl2, 82% (d) i.) cis-2-butene, n-BuLi, KOt-Bu, THF ii.) (+) Ipc2BOMe iii.) BF3·OEt2 then 10, >20:1 d.r. (e) TBSCl, imid., DMF, 87% over 2 Steps (f) 9-BBN, THF then I2, NaOCH3, MeOH, 85% (g) THF, DMPU, LiCCTMS, then KOH, MeOH, 81% (h) TiCl4, EtN(i-Pr)2, NMP, CH2Cl2, single diastereomer, 90%, (i) TBSOTf, 2,6-lutidine, CH2Cl2, 96% (j) DIBAL-H, CH2Cl2, 87% (k) 10 mol% (S,S) ProPhenol, Me2Zn, toluene, 88%, 95% ee (l) LiOH, THF, H2O then CuCl, CH3CN, 75% (m) MsCl, Et3N, CH2Cl2, 95%.