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. Author manuscript; available in PMC: 2008 Apr 30.
Published in final edited form as: Bioorg Med Chem Lett. 2007 Feb 2;17(9):2634–2638. doi: 10.1016/j.bmcl.2007.01.096

Scheme 3.

Scheme 3

Reagents and conditions: (a) 5-hexynoic acid, n-BuLi (2 equiv), HMPA, 5°C for 1 h, then 23°C for 12 h; CH2N2, 5% MeOH/Et2O, 23°C, 1 h, 60–65%; (b) PhC(O)Cl, DMAP, Et3N, CH2Cl2, 23°C, 12 h, 93%; (c) Me3SiCH2CH=CH2/BF3·Et2O, CH2Cl2, 23°C, 18 h, 80–82% (α-/β-isomers combined); (d) steps d-i in Scheme 1; (e) LiOH, THF/H2O (3:1), 23°C, 10 h, 92–96%; (f) DEAD/PPh3/PhCO2H, THF, 1 h, 0°C, 90–93%.