Synthesis of analogs of MIPP (compound 2). The specific substituents at R1, R2, R3 and Ar for each numbered compound are listed in the chart. For A–D, the specific conditions and reagents were as follows: (A) piperidine, CH3OH, reflux, 19 – 89%; (B) BBr3, CH2Cl2, – 78 °C, 61% and 95% for 15 and 21, respectively; (C) POCl3, DMF, 0 °C, 90%; piperidine, CH3OH, reflux, 89% ; (D) NaH, CH3I, DMF, RT, 82%.