Synthesis of the pyridyl “IN” fragment 32.
Reagents and Conditions: (a) PTSA, EtOH, 80 ° C, 100%; (b) NaBH4, EtOH, 80 ° C, 53%; (c) NH4OH, EtOH; (d) POCl3, DMF, 0 ° C; (e) potassium phthalimide, DMF, 69% over three steps; (f) H2NNH2-H2O, MeOH, THF; (g) Boc2O, Et3N, CH2Cl2, 43% over 2 steps; (h) α-methyl-L-cysteine, NaHCO3, pH 6.0 buffer, MeOH, 70 ° C, 84%.