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. Author manuscript; available in PMC: 2011 Jun 26.
Published in final edited form as: Tetrahedron. 2010 Jun 26;66(26):4745–4759. doi: 10.1016/j.tet.2010.03.093

Scheme 21a.

Scheme 21a

aConditions: (a) HF·NEt3 (46:54), CH3CN, rt, 1 h, >99%; (b) TIPSOTf, lutidine, CH2Cl2, −78 to 0 °C, 2 h, >99%; (c) MgBr2, n-BuSH, MeNO2, Et2O, 0 °C to rt, 1–3 h.