Minor coumarins from Calophyllum teysmannii var. inophylloide and synthesis of cytotoxic calanone derivatives

A chemotaxonomic survey for biologically active compounds from Malaysian Calophyllum species led to the finding of the four new benzoylcoumarins 1a, 2, 3, and 4a (including the unusual prenylated 6-benzoylcoumarin la), two uncommon coumarins 5 and 6a with a pyran-4-one moiety fused at C(6) and C(7), and compounds 7a, 9, and 10, all isolated from the bark of C. teysmannii var, inophylloide. Their structures were determined by spectroscopic analysis and chemical transformations. X-Ray crystal-structure determination of 2 provided information on the conformational preferences of substituents in this class of coumarins. The syntheses of the cytotoxic calanone (7a) and of some related coumarins are described.