Synthesis and degradation of novel photocrosslinkable aromatic copolyanhydrides

Novel photocrosslinkable degradable aromatic copolyanhydrides have been prepared by melt-polycondensation from 1,6-bis(p-carboxyphenoxy)hexane (CPH) and 4,4′-(sebacoyldioxy)dicinnamic acid (CSC) derived from 4-hydroxycinnamic acid and sebacoyl chloride. FT-IR and ¹H NMR confirmed the copolymer structures. These copolymers were subsequently irradiated with a 400 W high-pressure mercury lamp (λ > 28 nm) to produce crosslinked materials. The gel yields of copolymers increased with increasing irradiation time and/or CSC contents. The photocrosslinking significantly enhanced the tensile strength at break (σ_b) and tensile modulus (E), but decreased the elongation at break (ε_b). The crosslinked CPH/CSC(25/75) film with gel content of 90% showed the highest σ_b of 28 MPa and E of 742 MPa. The degradation characteristics of copolymer films was investigated in a phosphate buffer solution (pH 7.2 and 10.0) at 37 °C by mass loss, molecular weight reduction by GPC and contact angle measurement. The induction period was detected for all copolyanhydrides, and the rate of degradation of copolyanhydrides was much higher than that of PCPH.     

Total synthesis and determination of the absolute configuration of paralemnolin C and biological studies of eremophilane derivatives

The first asymmetric total synthesis of paralemnolin C was achieved. The absolute configuration at C11 of this natural product was determined from the X-ray crystallographic analysis of the epoxide derivative. In addition, biological studies of eremophilane derivatives including paralemnolin C and sagittacin E were carried out.     

Synthesis of Firefly Luciferin Analogues and Evaluation of the Luminescent Properties

Five new firefly luciferin ( 1 ) analogues were synthesized and their light emission properties were examined. Modifications of the thiazoline moiety in 1 were employed to produce analogues containing acyclic amino acid side chains ( 2 – 4 ) and heterocyclic rings derived from amino acids ( 5 and 6 ) linked to the benzothiazole moiety. Although methyl esters of all of the synthetic derivatives exhibited chemiluminescence activity, only carboluciferin ( 6 ), possessing a pyrroline‐substituted benzothiazole structure, had bioluminescence (BL) activity (λ_max=547 nm). Results of bioluminescence studies with AMP‐carboluciferin (AMP=adenosine monophosphate) and AMP‐firefly luciferin showed that the nature of the thiazoline mimicking moiety affected the adenylation step of the luciferin–luciferase reaction required for production of potent BL. In addition, BL of 6 in living mice differed from that of 1 in that its luminescence decay rate was slower.     

Concentration determination of oxygen nanobubbles in electrolyzed water

Water electrolysis is well known to produce solutions supersaturated with oxygen. The oxygen in electrolyzed solutions was analyzed with a dissolved oxygen meter and the Winkler method of chemical analysis. The concentration of oxygen measured with the dissolved oxygen meter agreed with that obtained using the Winkler method. However, measurements using a 10-fold dilution method showed a larger concentration of dissolved oxygen compared to the above methods. We developed a modified Winkler method to measure total oxygen concentration more accurately, which agreed with the results obtained from the 10-fold dilution experiment. The difference in measurements is due to the existence of oxygen nanobubbles, as confirmed by the observation of dynamic light scattering using a laser. Further analysis of the oxygen nanobubbles demonstrated that the stability of the nanobubbles was sufficient for chemical reaction and solvation to bulk solution.     

Diastereoselective Control of Tetraphenylethene Reactivity by Metal Template Self-Assembly

The reaction of 4,4′,4′′,4′′′-(ethene-1,1,2,2-tetrayl)tetraaniline with 2-pyridinecarboxaldehyde and iron(II) chloride resulted, after aqueous workup, in the diastereoselective formation of an [Fe₂L₃]⁴⁺ triple-stranded helicate structure, irrespective of the stoichiometry employed. The helicate structure was characterized in solution by multinuclear NMR spectroscopy, and in the solid state by single-crystal X-ray crystallography. The reaction of iron(II) tetrafluoroborate or iron(II) bistriflimide with the tetraaniline and 2-pyridinecarboxaldehyde allowed the formation of an [Fe₈L₆]¹⁶⁺ cube when the appropriate stoichiometry was used, but these structures were unstable with respect to hydrolysis. The pendant amine groups on the helicate can be functionalized by reaction with acid chlorides or anhydrides, and the resulting functionalized tetraphenylethene (TPE) units were isolated by the reaction of the helicate with tris(2-aminoethyl)amine. The emission properties of the TPE units were studied in THF/water mixtures, and they were found by dynamic light scattering to self-assemble into large (av. diameter 250 nm) structures.