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Reinvestigation of the fermentation broth and mycelium of the fungus Phoma herbarum led to the isolation of a new phytotoxic nonenolide, namely, (7R,9R)-7-hydroxy-9-propyl-5-nonen-9-olide, which was designated with the trivial name herbarumin III (3). The known compounds herbarumins I (1) and II (2) were also obtained. The structure of 3 was elucidated by spectroscopic methods and molecular modeling. Compounds 1-3 interacted with bovine-brain calmodulin and inhibited the activation of the calmodulin-dependent enzyme cAMP phosphodiesterase.

The (6'S)-configuration of brevipolides A-J (1-10), isolated from Hyptis brevipes, was established by X-ray diffraction analysis of 9 in conjunction with Mosher's ester analysis of the tetrahydro derivative 11 obtained from both geometric isomers 8 and 9 as well as by chemical correlations. The structure of the new brevipolide J (10) was characterized through NMR and MS data as having the same 6-heptyl-5,6-dihydro-2H-pyran-2-one framework possessing the cyclopropane moiety of all brevipolides but substituted by an isoferuloyl group instead of the p-methoxycinnamoyl moiety found in 8 and 9. Conformational analysis of these cytotoxic 6-heptyl-5,6-dihydro-α-pyrones was carried out on compound 9 by application of a protocol based on comparison between experimental and DFT-calculated vicinal (1)H-(1)H NMR coupling constants. Molecular modeling was used to correlate minimum energy conformers and observed electronic circular dichroism transitions for the isomeric series of brevipolides. Compounds 7-10 exhibited moderate activity (ED(50) 0.3-8.0 μg/mL) against a variety of tumor cell lines.

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The stems of Bursera suntui afforded two new verticillane derivatives, (1S,3Z,7E,11S,12S)-(+)-verticilla-3,7-dien-12,20-diol (1) and (1S,3Z,7E,11S,12S)-(+)-verticilla-3,7-dien-12,20-diol 20-acetate (2), together with (1S,3E,7E,11R)-(+)-verticilla-3,7,12(18)-triene (3), (1R,3E,7E,11R,12Z)-(+)-verticilla-3,7,12-triene (4), (1R,7E,11Z)-(-)-verticilla-4(20),7,11-triene (5), and (1S,3E,7E,11S,12S)-(+)-verticilla-3,7-dien-12-ol (6). Compounds 3 and 4 are new enantiomerically pure natural products whose racemic mixtures, derived from synthetic approaches toward the taxane skeleton, were obtained previously. The stems of Bursera kerberi afforded the new (1S,3E,7E,11S,12R)-(+)-verticilla-3,7-dien-12-ol (7) together with 3-5. This is the first time that verticillane derivatives have been isolated from the genus Bursera. Their structures and stereochemistry were elucidated by 1D and 2D NMR data, including COSY, NOESY, HSQC, and HMBC experiments, while the absolute configuration was determined by comparison of the optical rotatory dispersion data with that of recently revised (1S,3E,7E,11S,12S)-(+)-verticilla-3,7-dien-12-ol (6), obtained from Sciadopitys verticillata, and those of (1R,3E,7E,11R,12R)-(-)-verticilla-3,7-dien-12-ol (8) and (1R,3E,7E,11R,12S)-(-)-verticilla-3,7-dien-12-ol (9), isolated from the liverwort Jackiella javanica. The conformational preferences of 1-7 were studied by molecular mechanics modeling employing the Monte Carlo protocol.