Reagents and conditions:
(a)
(i) NBS, NH4Ac, MeCN, 0°C to RT, 12 h;
(ii) 5% HCl, NaOH, pH > 10, H2O, 0 °C,
20 min 91%; (b) (i) BH3-THF, THF, 0 °C to reflux, 12 h; (ii) 15% HCl in H2O,
0 °C to reflux, 3 h; (iii) NaOH, to pH > 12, 71%; (c) (i) CDI, DMF, RT; (ii) H2O, RT to reflux
to 0 °C, 20 min, 86%. (d) Boc2O, DMAP, THF, RT, 30 min, 97%; (e) (i) KOAc,
Pd(OAc)2, bis-(pinacolato)diboron, DMF; (ii) NaBO3·2H2O, THF/H2O; (f) (i) HCl/MeOH, RT to
60 °C, 1.5 h; (ii) NaHCO3, H2O, 0 °C, 5 h, 75%.