sordarin and sordaricin

Microbial transformation is known to be one of promising options to add functional groups such as a hydroxyl moiety to active base compounds to generate their derivatives. Sordaricin, a diterpene aglycone of the natural product sordarin, is an antifungal agent to selectively inhibit fungal protein synthesis by stabilizing the ribosome/EF-2 (elongation factor 2) complex. We screened actinomycetes to catalyze hydroxylation of sordaricin on the basis that the hydroxyl moiety would make it easier to generate derivatives of sordaricin. As a result of the screening, 6-hydroxylation of sordaricin was found to be catalyzed by Lentzea sp. 7887. We found that the cytochrome P450 inhibitor metyrapone inhibited this reaction, suggesting that a cytochrome P450 may be responsible for the biotransformation. As a next step, we cloned multiple cytochrome P450 genes, one of which were named P450Lent4B11, using degenerate PCR primers. The expressed cytochrome P450 derived from the P450Lent4B11 gene provided a different absorbance spectrum pattern from original one when it was incubated with sordaricin. Moreover, in cell-free conditions, the corresponding cytochrome P450 displayed the 6-hydroxylation activity toward sordaricin. Taken together, these results indicate that P450Lent4B11, derived from Lentzea sp. 7887, should be responsible for catalyzing 6-hydroxylation of sordaricin.

Topics: Actinomycetales; Antifungal Agents; Biotransformation; Cloning, Molecular; Cytochrome P-450 Enzyme System; Diterpenes; Fungi; Genes, Bacterial; Hydroxylation; Indenes; Metyrapone; Oxidation-Reduction

The first total synthesis of (-)-sordarin (1) was accomplished exploiting the following key reactions: (i) Ag(I)-catalyzed oxidative radical cyclization of a cyclopropanol derivative leading to a bicyclo[5.3.0]decan-3-one skeleton; (ii) Pd(0)-catalyzed intramolecular allylation reaction resulting in the entire strained bicyclo[2.2.1]heptan-2-one framework of sordaricin (2); (iii) selective dihydroxylation of terminal alkenes by the combined use of OsO(4) and PhB(OH)(2); and (iv) beta(1,2-cis)-selective glycosidation via a 1,3-anchimeric assistance from a 4-methoxybenzoyl group.

Topics: Biochemistry; Diterpenes; Indenes; Molecular Structure; Stereoisomerism

Rabbit pellets collected from the field were colonized by Podospora pleiospora at the exclusion of other coprophilous fungi, suggesting antibiosis. In liquid culture, P. pleiospora produced sordarin (1); sordarin B (2), a new compound in which sordarose is replaced by rhamnose; hydroxysordarin (3); and sordaricin (4). The major compounds 1 and 2 exhibited minimum inhibitory concentrations of 0.5-2.5 microg ml(-1) against the yeasts Nematospora coryli and Sporobolomyces roseus, but showed little or no activity against bacteria or coprophilous filamentous fungi. In liquid culture, the production of 1 and 2 together amounted to 2.7 microg ml(-1), whereas in rabbit dung only 1 was produced at a similar concentration (2.3 microg g(-1) fresh weight). The biosynthesis of these substances was unaffected by the presence of inoculum of other fungi tested (Sporobolomyces roseus or Penicillium claviforme) in liquid culture or on dung. Sordarin-type natural products are therefore synthesized by P. pleiospora at sufficiently high concentrations to account for antibiosis against yeasts, but not against filamentous fungi.

Topics: Animals; Antibiosis; Culture Media, Conditioned; Diterpenes; Indenes; Manure; Microbial Sensitivity Tests; Podospora; Protein Synthesis Inhibitors; Rabbits; Rhamnose; Soil Microbiology; Stereoisomerism; Yeasts

Oxime derivatives of the sordarin aglycone have been identified as potent antifungal agents. The in vitro spectrum of activity includes coverage against Candida albicans and Candida glabrata with MICs as low as 0.06 microg/mL. The antifungal activity was established to be exquisitely sensitive to the spatial orientation of the lipophilic side chains.

Topics: Antifungal Agents; Candida; Diterpenes; Hydrophobic and Hydrophilic Interactions; Microbial Sensitivity Tests; Oximes; Structure-Activity Relationship

Core-modified sordaricin derivatives were prepared via biotransformation followed by chemical modification and tested for antifungal activity. The antifungal activity proved to be very sensitive to modifications in the sterics and/or lipophilicity of the diterpene skeleton. Introduction of polar groups such as hydroxyl in the diterpene core results in loss of potency while small and lipophilic groups such as fluorine and the 7,8-olefin are well tolerated.

Topics: Antifungal Agents; Biotransformation; Candida albicans; Candida glabrata; Diterpenes; Hydrophobic and Hydrophilic Interactions; Microbial Sensitivity Tests; Nocardia; Stereoisomerism

Sordarin (1) was converted to 5 and 6, which showed potent antifungal activity against yeast. A series of C1-C9 alkyl side-chain derivatives was prepared, from which it was found that the optimal activity occurred with C5. A comparison of side chains with different unsaturation showed that the cis-alkene was the most active. This result suggested that the folding of the side chains might be crucial for the optimal activity.

Topics: Antifungal Agents; Diterpenes; Indenes; Indicators and Reagents; Microbial Sensitivity Tests; Molecular Conformation; Saccharomyces cerevisiae; Structure-Activity Relationship