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. Author manuscript; available in PMC: 2015 Dec 2.
Published in final edited form as: Bioorg Med Chem. 2014 Jan 23;22(5):1726–1735. doi: 10.1016/j.bmc.2014.01.017

Scheme 3.

Scheme 3

Reagents and conditions: (i) TBSCl, Et3N, DMF, 16 h, 65%; (ii) DAST, pyridine, CH2Cl2, 6 h, 31%; (iii) 2:1:1 H2O–THF–TFA, 20 min, 92%; (iv) NaH, H2NSO2Cl, dioxane, 16 h, 60%; (v) 9, Cs2CO3, DMF, 20 h; (vi) 4:1 TFA–H2O, 20 °C, 72 h, 4% from 18.