文摘
Antimalarial bioassay-guided fractionation of an EtOH extract of the root wood of Cryptocarya rigidifolia (Lauraceae) led to the isolation of the five new 5,6-dihydro-伪-pyrones cryptorigidifoliols A鈥揈 (1鈥?b>5) and the six bicyclic tetrahydro-伪-pyrone derivatives cryptorigidifoliols F鈥揔 (6鈥?b>11). The structure elucidations of all compounds were made on the basis of the interpretation of spectroscopic data and chemical derivatization, and the relative and absolute configurations were determined by NOESY, electronic circular dichroism (ECD), and 1H NMR analysis of 伪-methoxyphenylacetyl (MPA) derivatives. The bicyclic tetrahydro-伪-pyrone derivatives were identified as products of acid-catalyzed intramolecular Michael addition of the 5,6-dihydro-伪-pyrones in the presence of silica gel. A structure鈥揳ctivity relationship study suggested that the presence of an 伪,尾-unsaturated carbonyl moiety is not essential for potent antimalarial activity.