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. Author manuscript; available in PMC: 2013 Jul 15.
Published in final edited form as: Bioorg Med Chem. 2012 Jun 6;20(14):4217–4225. doi: 10.1016/j.bmc.2012.05.068

Scheme 1a.

Scheme 1a

a Reagents: (a) 1. Conc. H2SO4, EtOH, reflux; 2. toluene, Na, reflux, 3 h, ( 42% for 2 steps); (b) guanidine carbonate, t-butanol, potassium t-butoxide, μW, 4 h (34%); (c) 4-nitrobenzenesulfonylchloride, DMAP, Et3N, dichloromethane, rt.(36%); (d) 1,4-dioxane, substituted aniline, reflux, 12-18 h (18-59%).