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. Author manuscript; available in PMC: 2013 May 1.
Published in final edited form as: Chem Asian J. 2012 Mar 13;7(5):1052–1060. doi: 10.1002/asia.201101021

Scheme 4.

Scheme 4

Reagents and conditions: (a) 9 (2.0 equiv), Rh2(OOct)4 (2 mol%), hexanes, reflux, 95% for (±)-16, 90% for (−)-16 (dr 3:1); (b) DIBAL-H (7.5 equiv), CH2Cl2, −78 °C, then BF3•Et2O (1.5 equiv), CH2Cl2, −30 °C, 81% for (±)-17, 59% for (−)-17; (c) LDA (4.6 equiv), TMSCl (4.6 equiv), −78 °C to 0 °C; (d) mCPBA (1.1 equiv), NaHCO3,CH2Cl2, 0 °C, then (COOH)2 (4.6 equiv), 36%; 87% brsm.