Total Synthesis of (−)-Plicatic Acid (1)
a Conditions: (a) NaH, BnBr, quant. (b) (1) NMO, cat. OsO4; (2) NaIO4, quant. (c) N2CHCOOEt, cat. SnCl2, 92%. (d) 9, piperidine, PhCOOH, 80% (after one cycle), E/Z = 5:3. (e) (S,S)-TADOOH, cat. LiOH, 83%, 98% ee. (f) TfOH (0.04 eq.), 0 oC to r.t., 70% 2a, 17% 2b. (g) ClSi(Me)2CH2Br, imidazole, 75% (94% brsm). (h) SmI2, NiI2 (0.1 eq.), 0 oC, 58%. (i) H2O2, NaHCO3, 87% (90% brsm). (j) n-PrSNa, DMF, 97%. (k) H2, Pd/C, MeOH, then Dowex-50, 72%.