Fig. 7: Total synthesis from product 5a and 7b.
From: Catalytic enantioselective nitrone cycloadditions enabling collective syntheses of indole alkaloids
a Total syntheses of eburnane-type indole alkaloids. Reagents and conditions: (a) (Boc)2O, DMAP, Et3N, DCM, 25 °C; (b) Comins’ Reagent, LiHMDS, THF, −78 °C; (c) LiCl, Pd(PPh3)4, nBu3SnH, THF, 25 °C; (d) Allyl bromide, MeCN, 25 °C, then DABCO, reflux; (e) Grubbs II, DCM, reflux, then TFA, DCM, 0–25 °C; (f) LDA, HMPA, −78 °C, then EtI, THF, −40 °C; (g) DIBAL-H, Toluene, 0 °C; (h) LiAlH4, THF, 0–25 °C; (i) MsCl, Et3N, DCM, 0–25 °C; (j) TMSCN, TBAF, MeCN, 25 °C; (k) DIBAL-H, Toluene, −78 °C; (l) PtO2, H2, EtOH, 25 °C; (m) TPAP, NMO, DCM, 0–25 °C; (n) TFA, DCM, 0–25 °C. b Total syntheses of eburnane-type indole alkaloids. Reagents and conditions: (a) DIBAL-H, Toluene, −78 °C then HCl in MeOH, 0–25 °C; (b) PtO2, H2, MeOH, 25 °C; (c) DIBAL-H, Toluene, −78 °C then HCl in EtOH, 0–25 °C; (d) PtO2, H2, EtOH, 25 °C; (e) SO3•Py, DMSO, Et3N, 0 °C-25 °C; (f) TMSCN, AlCl3, CHCl3, 0–25 °C; (g) conc. HCl, MeOH, 80 °C; (h) LiAlH4, THF. 0–25 °C. c Total syntheses of (−)-arbornamine. Reagents and conditions: (a) LiAlH4, THF, 0–25 °C; (b) TBDPSCl, Imidazole, DMF, 25 °C; (c) SmI2, MeOH, THF, 25 °C; (d) (Z)-1-Bromo-2-iodo-2-butene, K2CO3, MeCN, 25 °C; (e) MsCl, Et3N, DCM, 0–25 °C; (f) TMSCN, TBAF, MeCN, 25 °C; (g) DIBAL-H, Toluene, −78 °C; (h) PDC, DCM, 25 °C; (i) LiHMDS, THF, PhSeBr, −78 °C, then aq. NH4Cl, H2O2, 0 °C; (j) Ni(COD)2, Et3N, Et3SiH, MeCN, 25 °C; (k) TBAF, THF, 0–25 °C, then LiAlH4, 0 °C.
