Scheme 1. Synthesis of 14.
Reagents and conditions: (a) n-BuLi, 27, THF, −78 °C, 63%. (b) Na2CO3, DMF, 110 °C, 93%. (c) 5 N HCl, THF, 55 °C, 100%. (d) Methyl azetidine-3-carboxylate hydrochloride, AcOH, DIPEA, NaBH3CN, MeOH/CH2Cl2, 71%. (e) Bis(di-tert-butyl(phenyl)phosphine) palladium dichloride (5 mol %), (2-fluorobenzyl)zinc chloride, THF, 85%. (f) LiOH, THF/H2O, then HCl and pH 6 sodium phosphate buffer, 99%.