Structure and stereochemistry of cyclobutatusin, a diterpenoid containing a four-membered ring

Abietane Diterpenes of the Genus Plectranthus sensu lato

Plectranthus (Lamiaceae), which—according to the latest systematic revision—includes three separate genera (Coleus, Plectranthus sensu stricto, and Equilabium), is a genus widely used in traditional medicine—mainly in the treatment of various ailments of the digestive tract, respiratory tract, and skin. Many species of Plectranthus s.l. have been shown to produce phenolic compounds and terpenes. Diterpenes, especially those of the abietane class, are the most studied group of secondary metabolites found in Plectranthus s.l., which is characterized by a significant structural diversity arising from the oxygenation and further rearrangement of the basic tricyclic abietane skeleton to a complete aromatization of the ring system. This review summarizes the known information on abietane diterpenes, showing their structures, sources, and biosynthesis. A classification of these compounds into nine groups, according to the arrangement of their ring C, is used. Royleanones, spirocoleons, and hydroquinones are the largest classes of abietane diterpenes, covering more than 70% of all the compounds reviewed.

Probing the Formation of Bicyclo[4.2.0]octan-1-ols

Reaction of lithium enolates of simple ketones with (+/-)-phenyl vinyl sulfoxide has potential for the convergent construction of complex fused ring systems containing a bicyclo[n.2.0]alkan-1-ol. The formation of sulfinylbicyclo[4.2.0]octan-1-ols 1-3 from the lithium enolate of cyclohexanone with (+/-)-phenyl vinyl sulfoxide or (R)-(+)-p-tolyl vinyl sulfoxide 18 was used to probe the mode of this novel cyclization reaction. Using phenyl vinyl sulfoxide, variations in the reaction lighting and solvent were investigated, in conjunction with radical trapping (TEMPO) and isotope labeling (deuterium) experiments. Cyclization to form sulfinylbicyclooctanols 1-3 is likely to proceed via an intermediate that ring closes to the bicycloalkanol anion 11 and was presently favored by the use of solvents such as THF or DME.