Structure determination of two new sesquiterpenoids from Streptomyces sanglieri
Sesquiterpenoids are a group of abundant and structurally diverse secondary metabolites mainly derived from plant and fungi. By contrast, they are rarely isolated from bacteria, and the terpene synthase genes had been considered to be silent in prokaryotes. Recently, more and more terpenes were identified from bacteria, and the biosynthesis of some terpenes has been discussed in heterologous bacteria. Actually, it demonstrated that the terpene synthases are widely distributed in bacteria, including streptomycete, and some new sesquiterpenoids and diterpenoids had been obtained through heterologous expression of terpene synthase genes derived from Streptomyces microorganism. In our ongoing investigation of new bioactive natural products from streptomycete, two new sesquiterpenes, 15-hydroxy-(+)-epicubenol (1) and 7β-hydroxy-7-epi-α-eudesmol (2), were identified from a fermentation broth of Streptomyces sanglieri (YIM 121209-2), which was isolated from the forest soil sample collected from Wuyi Mountain, Fujian Province, China. The structures of compounds 1 and 2 (Fig. 1) were elucidated based on detailed spectroscopic data analyses, including 1D and 2D NMR techniques. The cytotoxicity against two human cancer cell lines and antimicrobial activity against a panel of bacteria and fungi of 1 and 2 were evaluated. None of them showed cytotoxic or antimicrobial activities at 100μg/ml.
Epicubenol synthase and the enzymic cyclization of farnesyl diphosphate
Incubation of [1- 3 H]farnesyl diphosphate (2) with a cell-free extract obtained from Streptomyces sp. LL-B7 gave tritiated epicubenol (1), as confirmed by recrystallization of the derived triol 3 to constant activity. Cyclization of [13,13,13- 2 H 3 ]farnesyl diphosphate (2a) with crude epicubenol synthase gave [13,13,13- 2 H 3 ]epicubenol (1a), as established by 2 H NMR analysis. The existence of a 1,3-hydride shift was demonstrated by conversion of [1,1- 2 H 2 ]-farnesyl diphosphate (2b) to epicubenol (1b) which was shown by 2 H NMR to be labeled with deuterium at C-5 and C-11. These results can be explained by a proposed cyclization mechanism involving the intermediacy of nerolidyl diphosphate (4)
The Globalization problem for inner automorphisms and Skolem-Noether theorems
We investigate the circumstances under which an inner automorphism of a ring with local units can be built from “local” information. Specifically, we consider three natural “inner” type properties for an automorphism of a ring with local units. We show that every inner automorphism is locally inner but the converse is false, even if the automorphism is “piecewise” inner. On the other hand, we construct a large class of rings for which every locally inner automorphism is actually inner. Finally we obtain some Skolem-Noether type Theorems for infinite matrix and triangular matrix rings.