Scheme 3.
(a) (i) MsCl, Et3N, 0 °C → rt, 30 min, (ii) NaSMe, DMF, rt, 16 h, 76%; (b) (i) AcCl, MeOH, rt, 1 h, (ii), NaH, TBDMSCl, rt, 2 h, 75%; (c) (i) MsCl, Et3N, 0 °C → rt, 30 min, (ii) NaN3, DMF, 80 °C, 3 h, 80%; (d) NH2NH2•H2O, Pd black, MeOH, rt 1 h, 82%; (e) (i) aq. HCl (37%), MeOH, rt, 1 h, (ii) 10, NaCNBH3, NaHCO3, MeOH, (iii) 7M NH3-MeOH, 135 °C, sealed tube, 24 h, 20%; (f) NH2NH2•H2O, Pd black, 7M NH3-MeOH, rt 1 h, 54%.