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. Author manuscript; available in PMC: 2013 Sep 1.
Published in final edited form as: Bioorg Med Chem. 2012 Jul 14;20(17):5181–5187. doi: 10.1016/j.bmc.2012.07.006

Scheme 4.

Scheme 4

(a) (i) Amberlyst A26 (OH−) resin, MeOH; (ii) triphosgene, CH2Cl2, Et3N, rt, 90 min, 92%; (b) AcCl, MeOH, rt, 5 h, 93%; (c) (i) TsCl, pyridine, 0 °C → rt, 16 h; (ii) NaSMe, DMF, rt, 3 h, 44%; (d) KOH, i-PrOH, 80 °C, 4 h, 94%; (e) 10, AcCl, MeOH, NaCNBH3, rt, 3 h, 52%; (f) 7M NH3-MeOH, 135 °C, sealed tube, 24 h, 60%; (g) NH2NH2•H2O, Pd black, 7M NH3-MeOH, rt 1 h, 74%.