Longifolene synthesis, Corey

Scheme 13.20. Longifolene Synthesis E. J. Corey, R. B. Mitra, and P. A. Vatakencherry ...

Selectivity between secondary and tertiary alcohols by reagent Corey s longifolene synthesis Chemoselectivity in Enol and Enolate Formation... 

For example, in Corey s longifolene synthesis it was necessary to remove one ketone in the presence of another as shown below. Normally this would require protecting the ketone which is to remain. Both ketones are saturated, but they differ in steric environment. The total congestions calculated by SECS indicate that the ketone which is to remain is already protected by the... 

Longifolene synthesis E. J. Corey, R. B. Mitra, and P. A. Vatakencherry Longifolene synthesis J. E. McMurry and S. J. Isser Retrosynthetic analysis corresponding to synthesis in Scheme 13.19 Longifolene synthesis R. A. Volkmann, G. C. Andrews, and W. S. Johnson... 

Corey and co-workers developed an alternate approach to homologation of 6-merabered enones in their synthesis of longifolene. Selective ketaliza-tion of l,6-dioxo-8a-methyl-l,2,3,4,6,7,8,8a-octahydronaphthalene (25) " with... 

The first successful synthesis of longifolene was described in detail by E. J. Corey and co-workers in 1964. Scheme 13.19 presents a retrosynthetic analysis corresponding to this route. A key disconnection is made on going from I => II. This transformation simplifies the tricyclic skeleton to a bicyclic one. For this disconnection to correspond to a reasonable synthetic step, the functionality in the intermediate to be cyclized must engender mutual reactivity between C-7 and C-10. This is achieved in diketone II, because an enolate generated by deprotonation at C-10 can undergo an intramolecular Michael addition to C-... 

The total synthesis of longifolene represents a very serious challenge for the natural products chemist. The first synthesis was achieved by one of the greatest masters of the art, E.J. Corey of Harvard University.7 16,7 17... 

The logic centered approach leads to a restricted set of structures that may be converted in a single step to the target. Each new structure can. in turn, be converted to a new structure. The purpose of the retrosynthetic analysis is to generate synthetic intermediates (the synthesis tree) that terminate with a number of starting materials.Corey et al. outlined this approach in 1964 in his synthesis of longifolene (73), which is shown in Scheme 10.4.- 2 This synthesis used the 33 ieland-Miescher ketone (72) as the starting material. - Analyses... 

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