Scheme 14.

Cycloclavine (26). Reagents and conditions: (a) TBSOTf, Et₃N, CH₂Cl₂, 0 °C to room temperature, 45 min; (b) mCPBA, K₂CO₃, CH₂Cl₂, 0 °C, 2 h; (c) TBSCl, DMAP, imidazole, CH₂Cl₂, 6 h, 70% (3 steps); (d) ethyl diazoacetate, LDA, THF, −78 °C, 2 h, 79%; (e) SnCl₄, CH₂Cl₂, 0 °C, 10 min, 80%; (f) trimethylsilyl methylglycinate (133), PhMe, 0 °C, 30 min then 120 °C, 30 min, 65%; (g) DBU, H₂O, THF, reflux, 19 h; (h) TsCl, Bu₄NHSO₄, KOH, PhMe, 78% (2 steps); (i) DIBAL-H, PhMe, 0 °C to room temperature, 30 min; (j) Et₂Zn, I₂, CH₃I, CH₂Cl₂, 0 °C to room temperature, 24% (2 steps); (k) MsCl, NEt₃, 0 °C, 1 h; (l) LiBHEt₃, THF, 0 °C, 45 min; (m) NaOH, MeOH, reflux, 21% (3 steps)