Scheme 1. Synthesis of 1,6-naphthyridinone core scaffold by a divergent synthetic route. (i) Boc2O, DMAP, TEA, DCM, rt, 2 h. (ii) tBuLi, DMF, THF, –76 °C – rt, ovn. (iii) Ethylene glycol, p-TsOH, toluene, reflux, ovn. (iv) Benzylmagnesium chloride, THF, 0 °C – rt. (v) Sodium methoxide, MeOH, 65 °C, 4 h. (vi) HClaq, reflux, 3 h.
