Synthesis of ring fluoro ligand, 17a.
aReagents and conditions: (i) NBS, AcOH; (ii) NaOH, CuSO4; (iii) 1) TMSCHN2; 2) Cs2CO3, 1,2-dibromoethane, DMF, 80 °C, 16 h; (iv) HNO3 - 50 °C, 16 min; (v) 10% Pd/C, HCOOK, MeOH, 80 °C, 2 h; (vi) 1) CbzCl, aq. NaHCO3; 2) CDI, MeCN, rt, 2 h; 3) lithium (1-butylpiperidin-4-yl)methanolate, THF, 0 °C, then rt overnight; 4) H2, Pd/C.