Scheme 17.^a.

^a Reagents and conditions: (a) TBSCl, imidazole; (b) 192, NaH, Cl₃CCN, 0 °C; (c) TfOH, THF, 0 °C; (d) L-selectride, CH₂Cl₂, −78 °C; (e) HCl·H₂NOBn, py; (f) TBSOTf, 2,6-lutidine, CH₂Cl₂, 0 °C; (g) HF·py, THF; (h) TPAP, NMO, 4Å MS; (i) 1-amino-2-phenylaziridine, EtOH, 0 °C; (j) Ph₃SnH, AIBN, PhH, 78 °C; (k) SmI₂, THF, then TFAA; (l) PCC, CH₂Cl₂, 55 °C; (m) BF₃·Et₂O, CH₂Cl₂; (n) K₂CO₃, MeOH.