- Intramolecular regioselective insertion into unactivated prochiral carbon-hydrogen bonds with diazoacetates of primary alcohols catalyzed by chiral dirhodium(II) carboxamidates. Highly enantioselective total synthesis of natural lignan lactones
-
Intramolecular insertion into unactivated prochiral C-H bonds of 3-aryl-1-propyl diazoacetates catalyzed by dirhodium(II) tetrakis[methyl 1-(3-phenyl propanoyl)imidazolidin-2-one-4(R or S)-carboxylate], Rh2(4R-MPPIM)4 or Rh2(4S-MPPIM)4, occurs in 91-96% ee and with virtually complete regiocontrol for the formation of β-benzyl-γ-butyrolactones. This methodology has been applied to the total synthesis of dibenzylbutyrolactone lignans (-)- and (+)-enterolactone, (-)- and (+)-hinokinin, and (+)-arctigenin from substituted cinnamic acids in 19-27% overall yields. Aryltetralin lignan (+)-isodeoxypodophyllotoxin was prepared from the reactant 3,4-(methylenedioxy)cinnamic acid in 36% yield overall, and the lactone precursor to (+)-isolauricerisinol was formed in 96.5% ee and 23% yield overall. Applications of the chiral Rh2(MPPIM)4 catalysts to fully aliphatic systems resulting in the formation of β-substituted-γ-butyrolactones with high regiocontrol and with 93-96% ee have demonstrated the generality of this methodology. A model that provides accurate predictions of β-substituted-γ-butyrolactone absolute configurations in these asymmetric metal carbene transformations is described.
- Bode,Doyle,Protopopova,Zhou
-
p. 9146 - 9155
(2007/10/03)
-
- FIRST TOTAL SYNTHESIS OF (-)-α-CONIDENDRIN
-
Regioselective introduction of a benzoxy group, in the benzylic position of the β-benzyl-γ-butyrolactone (R)-(+)-8, was achieved by treatment with NBS followed with benzyl alcohol. α-Alkylation of the lithium enolate of the resulting intermediate 11, with
- Boissin, Patrick,Dhal, Robert,Brown, Eric
-
p. 4371 - 4374
(2007/10/02)
-
- THE SYNTHESES OF (R)-(+)-β-VANILLYL-γ-BUTYROLACTONE AND OF CHIRAL LIGNANS THEREFROM
-
(R)-(+)-β-vanillyl-γ-butyrolactone was obtained in 4 steps including a resolution, from vanillin and dimethyl succinate, and was used for the total syntheses of 5 naturally occurring and optically active lignans such as (+)-isolariciresinol 20.
- Brown, Eric,Daugan, Alain
-
p. 1169 - 1172
(2007/10/02)
-