Reagents
and conditions: (a) Br2, AcOH, rt, 80%; (b) SOCl2, MeOH, reflux, 77%; (c) NaN3, MeOH–H2O, rt, 91%; (d) 1. PPh3, CH2Cl2,
rt; 2. AcOH, THF–H2O, reflux, 66% for 2 steps; (e)
LiOH, MeOH–H2O, rt, 91%; (f) NBS, CH3CN–H2O–acetone, rt, 79%; (g) H2SO4 (cat.), MeOH, reflux, 95%.