Analysis of the kinetics of isomerization of spiro oxindole alkaloids
The isomerization of the spiro oxindole alkaloids mitraphylline, isomitraphylline, pteropodine, isopteropodine, speciophylline and uncarine F in water has been studied at several temperatures and the rate coefficients have been determined. The effect of pH on the rate of reaction and the equilibrium composition has been investigated. The rate coefficients in water and in organic solvents correlate satisfactorily with the Dimroth-Reichardt solvent polarity parameter. The present results support the existence of a zwitterionic intermediate stabilized by polar solvents and show that protonation of the alkaloids inhibits the isomerization. The crystal structure of pteropodine has been determined.
Laus, Gerhard,Broessner, Dagmar,Senn, Gilbert,Wurst, Klaus
p. 1931 - 1936
(2007/10/03)
New methods for the synthesis of oxindole alkaloids. Total syntheses of isopteropodine and pteropodine
The 2-oxindole alkaloids isopteropodine (11) and pteropodine (12) were conveniently synthesised from the known pentacycle (9) via a new and general protocol for oxidation and rearrangement of carboline lactams into 3,3-disubstituted-2-oxindoles.
Martin, Stephen F.,Mortimore, Michael
p. 4557 - 4560
(2007/10/02)
Transformation of indole alkaloids. I. Conversion of oxindole alkaloids into indole alkaloids
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Aimi,Yamanaka,Endo,et al.
p. 2015 - 2021
(2007/10/04)
Stereochemistry of oxindole alkaloids
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Pousset,Poisson,Shine,Shamma
p. 2766 - 2779
(2007/10/04)
Yohimbane derivatives. 3. The oxidative rearrangement of indole alkaloids to their spirooxindole analogs.
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Zinnes,Shavel Jr.
p. 1765 - 1771
(2007/11/06)
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