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BUTENOLIDE ANNELATIONS USING A MANGANESE(III) OXIDATION - A SYNTHESIS OF JOLKINOLIDE-E

1995-01-01
DEMIR, AS
Tanyeli, Cihangir
AKGUN, H
CALISKAN, Z
OZGUL, E
A general procedure was developed for the annelation of a butenolide to an enone that highlighted a manganese(III) oxidation of an enone. The merit of this procedure was illustrated in a synthesis of (-)-jolkinolide E, ent-1, from (+)-manool 11. A potassium permanganate-mediated degradation of 11 and dehydration of an intermediate beta-hydroxyketone 12 according to a literature procedure afforded a tricyclic enone 13. Oxidation of 13 with manganese(III) acetate and chloropropionic acid regio- and stereoselectively furnished a C-12 alpha chloropropionyl ester 14. An Arbuzov reaction of 14 with triethylphosphite and an intramolecular Horner-Emmons cyclization of the resulting phosphonate 15 gave (-)-jolkinolide E, the structure of which was investigated in detail by NMR. This methodology was also applied to 4,4-dimethylcyclohex-2-en-1-one. This overall approach offers a general solution to the problem of butenolide annelation to enones.