In the past, we have questioned the accuracy of the stereochemistry of elisabethatriene, a putative biosynthetic intermediate of pseudopterosins, in light of the configuration of elisabethatrienol isolated from Pseudopterogorgia elisabethae, which was represented as 1S,4R,9S,11S. We have reinvestigated the stereochemistry of elisabethatriene. Elisabethatriene with the reported 1S,4R,9R,11S configuration was synthesized starting from ( )-isopulegol in its enantiomeric form. The 1 H-and 13 C-NMR data of the synthesized compound differed from those reported for elisabethatriene. In addition to the fact that elisabethatriene is converted into pseudopterosins, this finding has allowed us to propose that elisabethatriene should have the 1S,4R,9S,11S stereochemistry, which is identical to that of elisabethatrienol.Key words elisabethatriene; elisabethatrienol; pseudopterosin; Pseudopterogorgia elisabethae Pseudopterosins are glycosylated tricyclic diterpenes isolated from marine octocoral, Pseudopterogorgia elisabethae, and more than thirty compounds in this class have been reported 1) since the first isolation of pseudopterosins A-D.2) Our group reported the isolation and characterization of pseudopterosins P-V as well as related non-glycosylated diterpenes, including elisabethatrienol (1) and seco-pseudopterosin K from P. elisabethae collected in San Andres and Providencia Islands in the Colombian Caribbean.3,4) It has been reported that pseudopterosin A displays potent anti-inflammatory activity 2) by inhibiting both phospholipase A2 and 5-lipoxygenase. 5)The biosynthesis of pseudopterosins was studied by Kerr's group. 6) These researchers reported the formation of a bicyclic compound named elisabethatriene (2a) upon incubation of geranylgeranyl diphosphate (GGPP) with a cell free preparation of P. elisabethae. Elisabethatriene has four stereogenic centers that were represented as 1S,4R,9R,11S (the pseudopterosin numbering system is applied). 7) These researchers also reported that incubation of elisabethatriene with the same preparation yielded erogorgiaene (3), 8) which was further converted to pseudopterosins 8) (Chart 1). Elisabethatrienol (1), a hydroxylated analogue of elisabethatriene, isolated by our group was determined to have the 1S,4R,9S,11S configuration on the basis of detailed nuclear Overhauser effect (NOE) experiments.4) It is of note that compounds elisabethatrienol and elisabethatriene have the opposite configuration at C-9, even though the stereogenic center disappears in the following intermediate 3. This finding raised the possibility that elisabethatriene could have the 1S,4R,9S,11S configuration (namely compound 4) rather than the reported 1S,4R,9R,11S configuration, since it would be reasonable to assume that the identical stereochemical mechanism is operating in the cyclization of GGPP leading to the two compounds. 4)In this article, we report the results from the reinvestigation of the stereochemistry that was reported for elisabethatriene. This study establishes that the stereochemistry o...

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A tripod molecule incorporating a C60 photocatalyst into a rigid scaffold with disulfide legs was designed and synthesized for the stable and robust attachment of C60 onto an Au-coated atomic force microscope (AFM) tip. The “tripod-C60” was immobilized onto the tip by forming S–Au bonds in the desired orientation and a dispersed manner, rendering it suitable for the oxidation and scission of single molecules on a countersurface, thereby functioning as “molecular shears”. A DNA origami with a well-defined structure was chosen as the substrate for the tip-induced oxidation. The gold-coated, C60-functionalized AFM tip was used for both AFM imaging and oxidation of DNA origami upon visible-light irradiation. The localized and temporally controlled oxidative damage of DNA origami was successfully performed at the single-molecule level via singlet-oxygen (1O2) generation from the immobilized C60 on the AFM tip. This oxidative damage to DNA origami can be carried out under ambient conditions in a fluid cell at room temperature, rendering it well-suited for the manipulation of a variety of species on surfaces via a spatially and temporally controlled oxidation reaction triggered by 1O2 locally generated from the immobilized C60 on the AFM tip.