Scheme (3) Synthetic pathways to analogs 14-59. Reagents and conditions: (a) Oxalyl chloride, DMF, CH₂Cl₂, rt (b) trimethylsilylazide, CCl₄, rt-50 ^oC (c) AcOH/HCl (d) RCO₂H, HATU, DIEA, MeCN (e) RSO₂Cl, NMI, Pyridine (f) RCHO, Na(OAc)₃BH, 1,2-DCE, rt