Scheme 3.
General synthetic procedures for compounds with 4-azetidinemethylene and 4-piperidinemethylene substituents. i) N-Boc-4-piperidinemethanol mesylate, Cs2CO3, DMF, 80 °C; ii) N-Boc-3-azetidinemethanol mesylate, Cs2CO3, DMF, 80 °C; iii) Na2CO3, Pd(PPh3)4, boronic acid or boronate pinacol ester, H2O/DME, 80 °C in microwave; iv) TFA/CH2Cl2 (1:1); v) sodium methoxide in MeOH, then 2% AcOH, R″-aldehyde, NaBH3CN; vi) Ac2O, TEA, DMF.