Investigation of conjugate addition/intramolecular nitrone dipolar cycloadditions and their use in the synthesis of dendrobatid alkaloid precursors

The sequential intramolecular conjugate addition of the oxime 13 followed by intramolecular dipolar cycloaddition of the intermediate nitrone 14 affords a mixture of the isoxazolidines 15, 16 and 17. The tricyclic 6,5,5-adduct 15 is believed to be the product of kinetic control and can be equilibrat...

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Bibliographic Details
Published in:Organic & biomolecular chemistry 2004-04, Vol.2 (8), p.1258-1265
Main Authors: Horsley, Helen T, Holmes, Andrew B, Davies, John E, Goodman, Jonathan M, Silva, María A, Pascu, Sofia I, Collins, Ian
Format: Article
Language:English
Subjects:
Alkaloids - chemical synthesis
Alkaloids - pharmacology
Chromatography, High Pressure Liquid
Cyclization
Indolizines - chemistry
Isoxazoles - chemistry
Ketones - chemistry
Kinetics
Nitrogen Oxides - chemistry
Oximes - chemistry
Stereoisomerism
Structure-Activity Relationship
Thermodynamics
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Summary:The sequential intramolecular conjugate addition of the oxime 13 followed by intramolecular dipolar cycloaddition of the intermediate nitrone 14 affords a mixture of the isoxazolidines 15, 16 and 17. The tricyclic 6,5,5-adduct 15 is believed to be the product of kinetic control and can be equilibrated with the epimeric tricyclic 6,5,5-isoxazolidine 17 through a beta-elimination/conjugate addition process. Conditions have been developed for the two-step conversion of the ketone 12 under thermodynamic control into the racemic tricyclic 6,6,5-adduct 16 which is the core precursor of all the known histrionicotoxin alkaloids.
ISSN:1477-0520
DOI:10.1039/b402307b