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Chiral synthons from carvone. Part 31. Enantiospecific total synthesis of (+)-2-pupukeanone and 5-epi-2-pupukeanone

Srikrishna, Adusumilli and Reddy, Jagadeeswar T (1998) Chiral synthons from carvone. Part 31. Enantiospecific total synthesis of (+)-2-pupukeanone and 5-epi-2-pupukeanone. In: journal of Chemical Society-Perkin Transacation, 1 (14). pp. 2137-2144.

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Abstract

The first enantiospecific total synthesis of (+)-2-pupukeanone and 5-epi-2-pupukeanone has been achieved starting from (R)-carvone, employing a radical cyclisation reaction based approach. (R)-Carvone has been transformed into the bicyclo[2.2.2]octenone 12 via kinetic alkylation, bromination of the isopropenyl moiety and intramolecular alkylation, which on further alkylation with prenyl bromide leads to bicyclo[2.2.2]octenone 16, The 5-exo-trig radical cyclisation of the bromohydrin 17, obtained from 16, furnishes an epimeric mixture of the isotwistanes 19 and 20 along with a minor amount of the rearranged product 21. Ozonolytic cleavage of the exomethylene moiety, dehydration of the tertiary alcohol and regioselective Wolff-Kishner reduction transforms the isotwistanes 19 and 20 into the enone 24, Alternatively, kinetic alkylation of the bicyclo[2.2.2]octenone 12 with 1,4-dibromo-2-methylbut-2-ene followed by 5-exo-trig allyl radical cyclisation of 35 and selective functional group transformations generates the isotwistane 23 and a minor amount of the rearranged product 29. Finally, catalytic hydrogenation transforms the enone 24 into (+)-2-pupukeanone 5 and its C-5 epimer 6.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Royal Society Chemistry.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Date Deposited: 13 Mar 2009 06:53
Last Modified: 19 Sep 2010 05:00
URI: http://eprints.iisc.ernet.in/id/eprint/18231

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