Methyl picrotoxate

The shade-dried sponges were extracted first with -hexane and then with ethyl acetate. The latter extract was evaporated to dryness and chomatographed on silica gel with benzene/ethyl acetate mixtures yielding 0.025% picrotoxinin (1), 0.003% methyl picrotoxate (42), and 0.017% picrotin (2) (7). 

Due to the more complex structures of most sesquiterpene picrotoxanes compared with the dendrobines, fewer syntheses have been reported. Their structures with up to nine stereogenic centers were too complex to be used as test molecules for newly developed reactions. Three of the syntheses reported beginning with 1979 followed new strategies (two picrotoxinin syntheses and one coriamyrtin synthesis). The other syntheses of picrotoxinin (1), picrotin (2), coriamyrtin (9), tutin (11), corianin (21), methyl picrotoxate (42), and asteromurin A (22) were extensions either of successful dendrobine syntheses or partial syntheses. Remarkably, with one exception, all the syntheses are EPC-syntheses. 

EPC-synthesis of methyl picrotoxate (42). Trost s syntheses were the last attempts toward sesquiterpene picrotoxanes. No efforts to s)mthesize C-18-or C-19-picrotox-anes ( norditerpene picrotoxanes) have been reported so far. 

A further intermediate of the above-described synthesis of picrotoxinin (1), diester 423, inspired the authors to attempt the first EPC-synthesis of methyl picrotoxate (42) (63). Originally, this compound was found as a degradation product of picrotoxinin (1) (2, 3). It was reported later as a minor constituent in both the plant M. cocculus and in the sponge S. inconstans. 

Pradhan P, Mamdapur VR, Sipahimalani AT (1990) Methyl Picrotoxate, a Minor Component of Berries of the Plant Anamirta cocculus and its Stereochemistry by High Resolution NMR Spectroscopy. Indian J Chem 29B 676... 

Krische MJ, Trost BM (1998) Total Synthesis of Methyl Picrotoxate via the Palladium Catalyzed Enyne Cycloisomerization Reaction. Tetrahedron 54 3693... 

Krische, M.J. and Trost, B.M. (1998) Total synthesis of methyl picrotoxate via the palladium catalyzed enyne cydoisomerization reaction. Tetrahedron, 54, 3693-3704. 

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