Investigation of Pimelea elongata ("Lakebed Pimelea") afforded 18 tigliane- and daphnane-type diterpenes (1-18). Eight of these were new compounds: four (1-3, 5) tigliane esters and four (7, 8, 10, 11) daphnane orthoesters. The 10 known compounds were 12-O-decanoylphorbol-13-acetate (4), P. simplex subtoxin B (6), wikstroelide E (9), pimelotides A and B (12, 13), gnidiglaucin (14), simplexin (15), huratoxin (16), kirkinine D (17), and 12-β-acetoxyhuratoxin (18). The structures and relative configurations of the new compounds were determined by 1D and 2D NMR spectroscopic studies in combination with MS analyses.

The cytochromes P450 are hemoproteins that catalyze a range of oxidative C-H functionalization reactions, including aliphatic and aromatic hydroxylation. These transformations are important in a range of biological contexts, including biosynthesis and xenobiotic biodegradation. Much work has been carried out on the mechanism of aliphatic hydroxylation, implicating hydrogen atom abstraction, but aromatic hydroxylation is postulated to proceed differently. One mechanism invokes as the key intermediate an arene oxide (and/or its oxepin tautomer). Conclusive isolation of this intermediate has remained elusive and, currently, direct formation of phenols from a Meisenheimer intermediate is believed to be favored. We report here the identification of a P450 [P450cam (CYP101A1) and P450cin (CYP176A1)]-generated arene oxide as a product of in vitro oxidation of tert-butylbenzene. Computations (CBS-QB3) predict that the arene oxide and oxepin have similar stabilities to other arene oxides/oxepins implicated (but not detected) in P450-mediated transformations, suggesting that arene oxides can be unstable terminal products of P450-catalyzed aromatic oxidation that can explain the origin of some observed metabolites.

An efficient route detailing the construction of the central core of pierisformaside C, the first grayanane-type diterpene to possess three central double bonds, is reported.

The major cuticular hydrocarbons from the cane beetle species Antitrogus parvulus were deduced to be 4,6,8,10,16,18-hexa- and 4,6,8,10,16-pentamethyldocosanes 2 and 3, respectively. Isomers of 2,4,6,8-tetramethylundecanal 27, 36, and 37, derived from 2,4,6-trimethylphenol, were coupled with the phosphoranes 28 and 29 to furnish alkenes and, by reduction, diastereomers of 2 and 3. Chromatographic and spectroscopic comparisons confirmed 2 as either 6a or 6b and 3 as either 34a or 34b. [structure: see text]