Total synthesis of gymnocin-A

A highly convergent total synthesis of gymnocin-A, a cyctotoxic polyether marine natural product, has been achieved. The synthesis features Suzuki-Miyaura coupling of the ABCD and FGHIJKLMN rings, stereoselective introduction of the C17 hydroxyl group, ring-closure of the F ring, and a late-stage incorporation of a 2-methyl-2-butenal side chain.     

Post-biotinylation of photocrosslinking by Staudinger-Bertozzi ligation of preinstalled alkylazide tag

Post-biotinylation of the alkyl azide derivative of trifluoromethyl phenyldiazirine (TPD) was elucidated to apply a photoaffinity biotinylation technique. A photo-modified polyvinilidene difluoride (PVDF) membrane was used as a photolabeled component and we introduced biotin by Staudinger-Bertozzi ligation. The 15 pmol amount of biotinylated reagent was still effective for the visualization of cross-linked product on the matrix. The results show the potential utility of alkyl azide carrying TPD derivatives in the application of photoaffinity biotinylation, which could be useful for the ligands with tight structural requirements.     

Synthesis and polymerization of 4-o-vinylbenzyl-2,2,6,6-tetramethylpiperidine

Some hindered amine polymers containing 2,2,6,6-tetramethylpiperidine structure were synthesized. A new monomer, 4-O-vinylbenzyl-2,2,6,6-tetramethylpiperidine, was homopolymerized and copolymerized with some vinyl monomers in the presence of AIBN as an initiator. The obtained amine polymers were oxidized with hydrogen peroxide to obtain the polymers having nitroxyl radical moiety.     

Hydrolysis of DNA by cerium(IV)/EDTA complex

Homogeneous solutions are formed from equimolar amounts of Ce(NH₄)₂(NO₃)₆ and EDTA. These solutions hydrolyze single-stranded DNA far more efficiently than double-stranded DNA. In contrast, Ce(IV) hydroxide gel, obtained in the absence of EDTA, hydrolyzes both single-stranded and double-stranded DNAs at almost the same rates. In order to achieve this substrate-specificity sufficiently, the mole ratio of EDTA to Ce(NH₄)₂(NO₃)₆ must be 1.0 or greater. By using this remarkable specificity of Ce(IV)/EDTA complex, gap-site in substrate DNA is selectively hydrolyzed. The scission-site is modulated by use of appropriate combination of oligonucleotide additives. The reactions have been kinetically analyzed.     

Coumarin-conjugated cyclodextrins: remarkable enhancement of the chemical-to-light energy transfer efficiency

One or two coumarin units were incorporated to the primary face of γ-cyclodextrin (γ-CD), and the resultant coumarin derivatives were employed to harvest the chemical energy generated in the reaction of bis(trichlorophenyl)oxalate with hydrogen peroxide. In comparison with the coumarin without CD cavity for molecular recognition, the coumarin–CD conjugates demonstrated much higher chemiluminescence inetensity, indicating that the CD moiety remarkably improves the chemical energy transfer.     

Metal-metal d-d interaction through the discrete stacking of mononuclear M(II) complexes (M = Pt, Pd, and Cu) within an organic-pillared coordination cage

Two molecules of planar MII(acac)2 complexes (M = Pt, Pd, and, Cu; acac = acetylacetonato) are efficiently stacked within an organic-pillared coordination cage, exhibiting characteristic spectroscopies (for M = Pt and Pd) and electron spin-spin coupling (for M = Cu) attributable to metal-metal interaction.     

Parallel synthesis of tandem Ugi/Diels-Alder reaction products on a soluble polymer support directed toward split-pool realization of a small molecule library

A series of parallel reactions were carried out for the tandem Ugi/Diels-Alder reaction on our MPEG-O-CH₂- platform. Ninety-six out of a 100 entries were successful to give complex heterotricycles. The stereoselectivity was found not to be influenced by the building blocks used for amine and carboxylic acid components. An unexpected side pathway was found but was suppressed by employing appropriate reaction conditions. The reaction was also performed on solid phase, by which a larger library is potentially realized by employing the split-pool method.     

Metal-dependent regioselective oxidative coupling of 5,10,15-triarylporphyrins with DDQ-Sc(OTf)3 and formation of an oxo-quinoidal porphyrin

[reaction: see text] Regioselectivity of the oxidative coupling of 5,10,15-triarylporphyrin metal complexes with DDQ-Sc(OTf)(3) was dependent on the central metal and meso-aryl substituent. Oxo-quinoidal porphyrin was obtained from Ni(II) porphyrin under the same conditions.     

Thermal stability of phthalate esters: Effect of substituents on the β-carbon atom

In order to clarify the mechanism conferring heat resistance on phthalate esters, those with a substituent on the β-carbon atom, such as bis(2-aminobutyl) phthalate, bis(2-nitrobutyl) phthalate, bis(2,4-diphenylbutyl) phthalate and dineopentyl phthalate, were synthesized and their thermal stabilities were studied by thermogravimetry and differential thermal analysis. The analytical results for these phthalate esters were compared with those for dibutyl phthalate, with a straight alkyl chain. As the temperatures required for a 3% weight loss of phthalate esters with a substituent, an electron-donating group (amino group) or an electron-accepting group (nitro group) on the β-carbon atom move to the higher end of the range, the effect of the adjacent group was recognized. The presence of a phenyl group in phthalate esters considerably improved the heat resistance. It is considered that the high heat resistance of bis(2,4-diphenylbutyl) phthalate is due to the obstruction of the planar configuration for cis elimination by the phenyl group and hindrance by the phenyl group of the formation of the six-membered cyclic transition state owing to the interaction between non-bondable molecules.     

Cross-linking chemistry and biology: development of multifunctional photoaffinity probes

An efficient method of photoaffinity labeling has been developed based on rationally designed multifunctional photoprobes. Photoaffinity techniques have been used to elucidate the protein structure at the interface of biomolecules by the photochemical labeling of interacting sites. However, the identification of labeled sites within target proteins is often difficult. Novel biotinyl bioprobes bearing a diazirine photophore have contributed significantly to the rapid elucidation of ligand binding sites within proteins, thereby extending conventional photoaffinity methods. This article discusses the synthesis and applications of various photoprobes bearing a biotin, including strategies using cleavable linkages between photophores. The combination of photoaffinity methods with chip technology is also described as a novel entry to rapid affinity-based screening of inhibitors. This review focuses on a rapid and reliable photoaffinity method utilizing diazirine-based multifunctional photoprobes with numerous potential applications in functional proteomics of biomolecular interactions.