Tetrazolo[1,5-a]pyridine-Containing π-Conjugated Systems: Synthesis, Properties, and Semiconducting Characteristics.

The incorporation of an electron-accepting unit into π-conjugated systems is an important approach to modulate the physical properties of such molecules. To investigate the potential of tetrazolo[1,5-a]pyridine as an electron-accepting unit, a series of diarylated tetrazolo[1,5-a]pyridine derivatives was synthesized by treating the corresponding diarylated pyridine N-oxide with diphenylphosphoryl azide. Thermogravimetric analyses of these molecules indicated that they possessed good thermal stability. The bithiophene-substituted tetrazolo[1,5-a]pyridine compound showed stable transistor characteristics under repeated bias conditions.

A semisynthetic fusicoccane stabilizes a protein-protein interaction and enhances the expression of K+ channels at the cell surface.

Small-molecule stabilization of protein-protein interactions is an emerging field in chemical biology. We show how fusicoccanes, originally identified as fungal toxins acting on plants, promote the interaction of 14-3-3 proteins with the human potassium channel TASK-3 and present a semisynthetic fusicoccane derivative (FC-THF) that targets the 14-3-3 recognition motif (mode 3) in TASK-3. In the presence of FC-THF, the binding of 14-3-3 proteins to TASK-3 was increased 19-fold and protein crystallography provided the atomic details of the effects of FC-THF on this interaction. We also tested the functional effects of FC-THF on TASK channels heterologously expressed in Xenopus oocytes. Incubation with 10 µM FC-THF was found to promote the transport of TASK channels to the cell membrane, leading to a significantly higher density of channels at the surface membrane and increased potassium current.

Molecular breeding of a fungus producing a precursor diterpene suitable for semi-synthesis by dissection of the biosynthetic machinery.

Many clinically useful pharmaceuticals are semi-synthesized from natural products produced by actinobacteria and fungi. The synthetic protocols usually contain many complicated reaction steps and thereby result in low yields and high costs. It is therefore important to breed microorganisms that produce a compound most suitable for chemical synthesis. For a long time, desirable mutants have been obtained by random mutagenesis and mass screening. However, these mutants sometimes show unfavorable phenotypes such as low viability and low productivity of the desired compound. Fusicoccin (FC) A is a diterpene glucoside produced by the fungus Phomopsis amygdali. Both FC and the structurally-related cotylenin A (CN) have phytohormone-like activity. However, only CN exhibits anti-cancer activity. Since the CN producer lost its ability to proliferate during preservation, a study on the relationship between structure and activity was carried out, and elimination of the hydroxyl group at position 12 of FC was essential to mimic the CN-like activity. Based on detailed dissection of the biosynthetic machinery, we constructed a mutant producing a compound without a hydroxyl group at position 12 by gene-disruption. The mutant produced this compound as a sole metabolite, which can be easily and efficiently converted into an anti-cancer drug, and its productivity was equivalent to the sum of FC-related compounds produced by the parental strain. Our strategy would be applicable to development of pharmaceuticals that are semi-synthesized from fungal metabolites.

Transannular proton transfer in the cyclization of geranylgeranyl diphosphate to fusicoccadiene, a biosynthetic intermediate of fusicoccins.

Enzymatic cyclization of geranylgeranyl diphosphate to fusicoccadiene involves a transannular proton transfer process. Label distribution in the cyclized products derived from deuterium-labeled GGDPs showed that a proton generated from C-10 migrates to C-6 in the intermediary dolabellane framework prior to the second ring formation. Although a direct 1,5-proton transfer would achieve this process, semiempirical MO calculations suggested an alternative pathway, which involves successive 1,4- and 1,5-proton transfers using C-2 as a springboard.

A novel water-soluble Hantzsch 1,4-dihydropyridine compound that functions in biological processes through NADH regeneration.

A novel Hantzsch 1,4-dihydropyridine derivative could function in an organic solvent-free solution, and thus it could function in biological systems. These functions can be accomplished through regeneration of the reduced form of nicotinamine adenine dinucleotide (NADH), an essential compound for living organisms. The results obtained here demonstrate the usefulness of a water-soluble Hantzsch 1,4-dihydropyridine derivative and its wide applicability as a chemical energy source, which drives various biological processes efficiently.