Fig. 3: Evolution of strategies to functionalize the Δ6,7-alkene. | Nature Communications

Fig. 3: Evolution of strategies to functionalize the Δ6,7-alkene.

From: Divergent syntheses of complex Veratrum alkaloids

Fig. 3

a Attempted dihydroxylation of the Δ6,7-alkene. b Initial exploration of the neighboring-group participation strategy. c Analysis of the successful elimination reaction in 18. d The failed attempt to access the substrate with free C9-OH via a carbonate intermediate. Reagents and conditions: (a) OsO4, pyridine, 0 °C to rt, overnight, 85%. b AgOAc, I2, AcOH, overnight, 70%. c NaBH4, DCM/MeOH=1:4, 0 °C, 30 min, 82%. d NaHMDS, TBSCl, then Bz2O, THF, 0 °C, 1 h, 80%. e IBr, MeCN, buffer (pH = 7), 28 °C, 2 h, 85%. f AIBN, nBu3SnH, benzene, reflux, 1 h then TBAF, THF, rt, 2 h, 81%. g TsCl, pyridine, rt, 5 h, 90%. h NaHMDS, TBSCl, then Boc2O, THF, 0 °C, 1 h, 80%. i IBr, MeCN, buffer (pH = 7), 28 °C, 2 h, 80%.

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