Scheme 1. Reagents and conditions: (i) a) KOH, EtOH, RT.; (ii) b) Zn; NH4Cl, RT.; (iii) c) guanidine hydrochloride, KOH, H2O2, EtOH, reflux; (iv) d) (CH3)2SO4, NaOH, THF/H2O, RT.; e) NBS, CH3CN, –20 °C; f) CH3ONa, CuI, DMF/MeOH, reflux; g) DMF, POCl3, DCM, reflux; h) CH3I, Mg, Et2O, N2, HCl; i) MnO2, DCM, reflux; j) AlCl3, CH3CN; (v) k) KCN, NCCH2COOEt, KOH, DMF, 60 °C, NaOH–H2O (5%), reflux; l) Mg, CH3I, Et2O, N2, HCl.
