Scheme 5: Synthesis of compounds 10–27a.
a Reagents and conditions: a) HCOOMe, reflux (for 10,24); b) R2COCl, DIPEA, DCM or AcCN, rt (for 11,12,17, 25); c) R2COOH, TBTU, THF (for 13,14,16); d) (CF3CO)2O, DCM, 0°C-rt (for 15); e) rac-BrCH(CH3)CONH2, DMF (for 18); f) R1SO2Cl; DIPEA, DCM, rt (for 19,20,21,23,26); g) CbzNHSO2Cl, DIPEA, DCM and h) Pd/C, MeOH, ammonium formate (for 22,27).