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[reaction: see text] A strategy for synthesis of the hexahydroxanthene moiety of the natural products schweinfurthin A, B, and D is described. The relative stereochemistry in the key cationic cyclization step is established through the preference of the phenylselenide substituent for an equatorial orientation.

Salicortin, a natural product abundant in most members of the Salicaceae family, is a mechanism-based inactivator of Agrobacterium faecalis beta-glucosidase. Inactivation is delayed in the presence of competitive inhibitors, thereby demonstrating the requirement for an enzyme-bound salicortin before inactivation. Product studies suggest that inactivation proceeds via a quinone methide intermediate formed by the fragmentation of the aglycone of salicortin while it is bound to the enzyme. Tryptic digest and HPLC/MS studies confirm the role of quinone methide attack and also show that the enzyme undergoes multiple modifications. In addition, when the inactivation was run in the presence of a mutant inactive form of the enzyme, HPLC/MS analyses clearly showed no modification of the mutant enzyme, demonstrating that the quinone methide does not exist in free solution and suggesting that inactivation is active-site directed.

A new prenylated benzoic acid, arieianal [3,4-dihydroxy-5-(E,E, E-11'-formyl-3',7',15'-trimethylhexadeca-2',6',10', 14'-tetraenyl)benzoic acid, 1], has been isolated from the leaves of Piper arieianum and assigned this structure on the basis of its spectral data.

Key indicatorsSingle-crystal X-ray study T = 298 K Mean (C-C) = 0.003 Å R factor = 0.050 wR factor = 0.148 Data-to-parameter ratio = 12.2For details of how these key indicators were automatically derived from the article, seeThe molecular structure of (I), showing the atom-numbering scheme and displacement ellipsoids drawn at the 50% probability level.