Quantum yields and quantitative spectra of firefly bioluminescence with various bivalent metal ions

We measured quantitative spectra of firefly (Photinus pyralis) bioluminescence in the presence of Zn²⁺ and other bivalent metal ions to investigate the effects of these metal ions on luciferin‐luciferase reaction. We studied the dependence of the quantum yield and spectrum on quantity and kind of bivalent metal ions. Adding various amounts of Mg²⁺, Mn²⁺ and Ca²⁺ produced virtually no change in the quantum yields or the spectra of bioluminescence. In contrast, increasing amounts of ions such as Zn²⁺ and Cd²⁺ decreased quantum yields and changed the bioluminescence color from yellow‐green to red. Quantitative analysis showed that the sensitivities of the quantum yield and color to various metal ions were in the order of Hg²⁺>Zn²⁺, Cd²⁺>Ni²⁺, Co²⁺, Fe²⁺≫Mg²⁺, Mn²⁺, Ca²⁺. We propose that the changes in quantum yield and spectrum caused by the metal ions are due to their effect on luciferase that surrounds oxyluciferin during its radioactive decay. We also found that having more metal ions accelerated bioluminescence reactions. The sensitivity of the reaction rate had no correlation with those of the quantum yield and spectrum.     

Structural elucidation and regioselective functionalization of an unexplored carbide cluster metallofullerene Sc2C2@C(s)(6)-C82

A Sc(2)C(84) isomer, previously assumed to be Sc(2)@C(84), is unambiguously identified as a new carbide cluster metallofullerene Sc(2)C(2)@C(s)(6)-C(82) using both NMR spectroscopy and X-ray crystallography. The (13)C-nuclei signal of the internal C(2)-unit was observed at 244.4 ppm with a 15% (13)C-enriched sample. Temperature-dependent dynamic motion of the internal Sc(2)C(2) cluster is also revealed with NMR spectrometry. Moreover, the chemical property of Sc(2)C(2)@C(s)(6)-C(82) is investigated for the first time using 3-triphenylmethyl-5-oxazolidinone (1) which provides a 1,3-dipolar reagent under heating. Regarding the low cage symmetry of this endohedral which contains 44 types of nonequivalent cage carbons, it is surprising to find that only one monoadduct isomer is formed in the reaction. Single-crystal X-ray results of the isolated pyrrolidino derivative Sc(2)C(2)@C(s)(6)-C(82)N(CH(2))(2)Trt (2) reveal that the addition takes place at a [6,6]-bond junction, which is far from either of the two Sc atoms. Such a highly regioselective addition pattern can be reasonably interpreted by analyzing the frontier molecular orbitals of the endohedral. Electronic and electrochemical investigations reveal that adduct 2 has a larger highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap than pristine Sc(2)C(2)@C(s)(6)-C(82); accordingly, it is more stable.     

Polymerization of coordinated monomers. IV. Copolymerization of methyl methacrylate– and methacrylonitrile–Lewis acid complexes with styrene

Complexes of methyl methacrylate and methacrylonitrile with Lewis acids (SnCl₄, AlCl₃, and BF₃) were copolymerized with styrene at ?75°C under irradiation with a high-pressure mercury lamp in toluene solution. The resulting copolymers consisted of equimolar amount of methyl methacrylate or methacrylonitrile and styrene, regardless of the molar ratio of monomers in the feed. NMR spectroscopy showed the copolymers to have an alternate sequence. The tacticities of the copolymers varied with the complex to have an alternate sequence. The tacticities of the copolymers varied with the complex species: the copolymer from the SnCl₄ complex system had a higher cosyndiotactieity, while those from the AlCl₃ and the BF₃ complex systems showed coisotacticity to predominate over cosyndiotacticity. NMR spectroscopic investigation of the copolymerization system indicated the presence of a charge-transfer complex between the styrene and the methyl methacrylate coordinated to SnCl₄. The concentration of the charge-transfer complex was estimated to be about 30% of monomer pairs at ?78°C at a 1:1 molar ratio of feed. The growing end radicals were identified as a methyl methacrylate radical for the AlCl₃ complex–styrene system and a styrene radical for the SnCl₄ complex–styrene system by the measurement of the ESR spectra of the copolymerization systems under or after irradation with a high-pressure mercury lamp. The tacticity of the resulting polymer appears to be controlled by the structure of the charge transfer complex. In the case of the SnCl₄ complex a certain interaction of SnCl₄ with the growing end radical seems to be a factor controlling the polymer structure. These copolymerizations can be explained by an alternating charge-transfer complex copolymerization scheme.     

Synthesis of (+)-altholactone, (+)-7-epi-altholactone, (−)-etharvensin,and (+)-alumheptolide-A using Pd-catalyzed carbonylation

Syntheses of (+)-altholactone isolated from Goniothalamus giganteus and its C-7 epimer (+)-7-epi-altholactone, (?)-etharvensin and (+)-alumheptolide-A were achieved. The lactone ring of these compounds was constructed using Pd-catalyzed carbonylation.     

Synthesis of epigallocatechin trimer, (epigallocatechin)2-epicatechin,and (epigallocatechin)2-catechin via a Lewis acid mediated one-pot condensation and their antitumor activities in prostate cancer cells

Syntheses of epigallocatechin trimer, (epigallocatechin)₂-epicatechin and (epigallocatechin)₂-catechin were achieved. The key condensation to form the proanthocyanidin trimer derivatives was accomplished in a one-pot procedure using a dimeric epigallocatechin electrophile, which was prepared in situ by self-condensation of an epigallocatechin derivative, and an epigallocatechin, epicatechin, or catechin derivative as the nucleophile in the presence of a Lewis acid. The epigallocatechin monomer to trimer compounds containing a pyrogallol group significantly suppressed cell proliferation in PC-3 prostate cancer cells.     

General, robust, and stereocomplementary preparation of beta-ketoester enol tosylates as cross-coupling partners utilizing TsCl-N-methylimidazole agents

We have developed a general, robust, and cost-effective method for the (E)- or (Z)-stereocomplementary enol tosylation of beta-ketoesters using TsCl- N-methylimidazole (NMI)-Et3N or LiOH. TsCl coupled with NMI formed a highly reactive N-sulfonylammonium intermediate. Stereocongested secondary alcohols were smoothly sulfonylated using Ts(Ms)Cl-NMI-Et3N. beta-Ketoesters underwent (E)-selective tosylation using TsCl-NMI-Et3N and (Z)-selective tosylation using TsCl-NMI-LiOH (total of 23 examples; 60%-99% yield). Stereoretentive Negishi and Sonogashira couplings using enol tosylates proceeded successfully to give trisubstituted alpha,beta-unsaturated esters.