SYNTHESIS OF NATURALLY OCCURRING DIOSPHENOLS AND HYDROXYDIOSPHENOLS

ABSTRACT

Syntheses of diosphenol (3), ψ-diosphenol (4), 6-hydroxydiosphenol (5) and 6-hydroxy-ψ-diosphenol (6), which are constituents of the essential oil from Barosma betulina Bartl. (mountain buchu), are discussed.     

THE SPECTROSCOPY AND PHOTOCHEMISTRY OF ENAMINONITRILES INCLUDING THE SYNTHESIS AND IDENTIFICATION OF CIS-β-AMINOACRYLONITRILE

Abstract— The absorption spectral and photochemical properties of β-aminoacrylonitrile (AAN), β-aminocrotonitrile (ACN) and three other enaminonitriles have been studied. The synthesis and identification of cis -β-aminoacrylonitrile are also included. Each enaminonitrile has one intense absorption band (1–2 × 10⁴M^-1cm^-1) in the 254–273 nm region. Photoisomerization and photocyclization to imidazoles are observed. Imidazole formation is quite strongly inhibited by oxygen and the presence of oxygen can cause wavelength dependent photochemistry, other reactions and destruction of the reactant. The quantum yield of formation of imidazoles is low (<10^-4) for β-aminoacrylonitrile and β-aminocrotonitrile and photoisomerization dominates in those four cases where it can occur. Imidazole formation from a dimethylamino compound proves that the presence of H atoms on the amino group is not a prerequisite for photocyclization.     

SPECTROSCOPY AND PHOTOCHEMISTRY OF 8-SUBSTITUTED 5-DEAZAFLAVINS

Abstract— Absorption, fluorescence and phosphorescence spectra as well as fluorescence and phosphorescence quantum yields of 8-X-5-deazaflavins (X = C1, NO₂, p -NO₂-C₆H₄, N(CH₃)₂, NH₂, p -NH₂-C₆H₄, p -N(CH₃)₂-C₆H₄-N=N) were determined. It was found that all these data are highly influenced by the substituent at position 8 of the 5-deazaisoalloxazine skeleton. Also the photoreduction of 8-X-5-deazaflavins in the presence of electron donors was studied. It was established that the photoreduction leads to the formation of a 5,5'-dimer and/or a 6,7-dihydro compound. Reduction of the C(6)-C(7) bond is promoted by strong electron-donating substituents and bulky electron donors. 5-Deazaftavins with a reducible substituent at position 8 exhibit reduction of the substituent prior to the reduction of the 5-deazaisoalloxazine skeleton.     

TRIARYLMETHANE DYE PHOTOCHROMISM: SPECTROSCOPY AND PHOTOCHEMISTRY OF BRILLIANT GREEN LEUCOCYANIDE

Abstract— The spectroscopy and photochemistry of brilliant green leucocyanide 1a were investigated at room and low temperature, in polar and nonpolar solvents. At 77 K, 1a exhibits solvent independent absorption, fluorescence (φ _f = 0.1), and phosphorescence (φ _p = 0.5). Solvent effects become important at room temperature; in polar solvents, φ _f , decreases and photodissociation yielding brilliant green dye 3 occurs [φ _dis ,(EtOH) ˜0.91. Dye formation and 1a fluorescence can be quenched by 0.1 M crotononitrile. Attempts to sensitize dye formation with triplet sensitizers were unsuccessful. The spectroscopy of 3 was also examined.     

SPECTROSCOPY AND PHOTOCHEMISTRY OF BILIRUBIN PHOTOPRODUCTS. I. METHYLVINYLMALEIMIDE*

Abstract— Methylvinylmaleimide, a product of the photooxidation of bilirubin, exhibits a broad luminescence band at approximately 450 nm on filter paper at room temperature. In methanol solvent, at 77 K, a broad phosphorescence band centered at 465 nm is observed. The experimental and theoretical spectroscopic properties of this compound are compared to those of the related molecules maleimide and phthalimide. Methylvinylmaleimide is photodegraded at pH 7.6 in a self-sensitized reaction that in part involves singlet oxygen.     

SPECTROSCOPY OF CHLOROPHYLL IN BIOLOGICAL AND SYNTHETIC SYSTEMS*

Abstract. –This review discusses recent spectroscopic studies aimed at discovering the structure, orientation, and function of chlorophyll in vivo. In plant membranes there appear to be at least two distinct types of chlorophyll a. The greater part, over 99%, is antenna chlorophyll which absorbs and transfers radiant energy to a few specialized chlorophyll molecules in a reaction center where the actual charge separation occurs. A dimer-oligomer model for antenna chlorophyll has been proposed on the basis of comparative studies of the absorption spectra of chlorophyll in various dry solvents and in vivo. Unfortunately a similarity between essentially structureless broad spectra is very weak evidence for their original identity. Also the requirement of an anhydrous environment for most of the chlorophyll in biological material is an unlikely postulate. A cross-linked, linear polymer model of chlorophyll in vivo has also been proposed. Recent Resonance Raman spectroscopic results appear to rule out, in large part, either polymer model and once again suggest that it is the various attachments of chlorophyll to proteins which determine its function as antenna pigment in vivo. Circular dichroism measurements of chlorophyll in various plant materials have also led to the conclusion that antenna chlorophyll has strong interaction with protein. However, some doubt still exists as to the interpretation of these CD results. New studies of fluorescence, polarized fluorescence and Resonance Raman spectroscopy of various plant species corroborate the original proposition, based upon deconvolution of absorption spectra, that antenna chlorophyll occurs in vivo in at least five discrete pools, and that each pool is likely to be located in the same environment in different plants. A new model-systems approach to simulating chlorophyll in vivo has come through the use of lipid bilayers and liposomes. Charge transfer has been observed between chlorophyll in a lipid phase and phycobiliproteins or cytochrome c. The most promising, newly synthesized model for the reaction center, P700, is a covalently bound dimeric derivative of pyrochlorophyllide a. Its properties are similar to P700 in several respects except for reversible photooxidation which has not yet been observed. By detergent treatments chlorophyll-protein complexes having about 20–40 chlorophyll a molecules for every P700 have been isolated from different plants, and their spectroscopic properties are under investigation in several laboratories. The several hypotheses to explain the shape of the oxidized minus reduced absorption difference spectrum of P700 have not yet been reconciled. The nature of the photosystem II reaction center chlorophyll, P680, is also a subject of active investigation. Its absorption difference spectrum appears to have two kinetic components.     

PHOTOCHEMISTRY AND SPECTROSCOPY OF CHLOROPHYLL, BACTERIOCHLOROPHYLL AND BACTERIOVIRIDIN IN MODEL SYSTEMS AND PHOTOSYNTHETIZING ORGANISMS

Abstract— In the system (electron donor—pigment—electron acceptor), the photosensitising pigment transfers an electron (hydrogen) from the donor to the acceptor by converting light energy, absorbed by the pigment, into the potential chemical energy of the products. The dependence of the reaction of excited pigments with electron donors or acceptors on the magnitude of the electron affinity of the reacting molecules, the nature of the medium, and the experimental conditions was observed. The initial photo-process was seen to involve the formation of free radicals, with the subsequent formation of compounds with saturated valencies. The reverse reaction of the photoproducts was accompanied by chemiluminescence. The study of systems containing pyridinenucleotides showed the possibility of photosensitised oxidation—reduction of these compounds by a pigment, and of direct photooxidation of reduced pyridinenucleotides by an electron acceptor of a different kind. In order to understand the specific photo-transfer of an electron in organisms, the spectral properties of pigments in organisms were compared with the properties of model pigments in monomeric and aggregated forms. It was established that the main role in the spectroscopic properties shown by bacteriochlorophyll, bacterioviridin and chloropyll in organisms is played by various types of intermolecular interactions (aggregations). Different forms of pigment may be involved in different stages of the phototransfer of an electron.     

PHOTOTOXIC EFFECTS OF NATURALLY OCCURRING POLYACETYLENES AND α-TERTHIENYL ON HUMAN ERYTHROCYTES

Hemolysis, K⁺ leakage and acetylcholinesterase (AChE) inhibition in human erythrocytes were observed with certain naturally occurring polyacetylenes and a thiophene derivative, α-terthienyl. K' leakage, subsequent hemolysis and AChE inactivation by phenylheptatriyne (PHT), a phototoxic compound, were considerably enhanced by UV light (312–400 nm). The same was true with α-terthienyl and with certain other polyacetylenes. Oxygen enhanced AChE inactivation and hemolysis with α-terthienyl in light. With PHT, only AChE inhibition was significantly enhanced in oxygen. Falcarindiol, a non-phototoxic polyacetylene, did not inactivate this enzyme but caused hemolysis in the dark. Inhibition of AChE and hemolysis by these compounds appear to be unrelated phenomena. These results indicate that certain polyacetylenes are capable of damaging biological membranes in light, and others in dark.     

INDUCTION OF CROSS-LINKS IN VIRAL DNA BY NATURALLY OCCURRING PHOTOSENSITIZERS

Abstract— Six different photosensitizers were compared for their ability to form cross-links in murine cellular DNA and murine cytomegalovirus DNA, in the presence of long wave UV radiation. The viral DNA was in the form of free DNA or intact virions. The compounds consisted of the linear furanocoumarins 8-methoxypsoralen (8-MOP) and isopimpinellin; the angular furanocoumarin, angelicin; the two furanochromones, visnagin and khellin; and the β-carboline alkaloid, harmine. Cross-linking was assessed by alkaline agarose gel electrophoresis and hydroxyapatite chromatography. 8-MOP produced extensive cross-linking (as expected), as did isopimpinellin. Visnagin produced less cross-linking, such that not all DNA molecules were affected at the concentrations used. Khellin, angelicin and harmine produced no detectable cross-linking. The same result was obtained for DNA which was treated in situ in the virion. To some degree there was a correlation between the amount of cross-linking and the relative potency of anti-MCMV infectivity. But other factors evidently contribute to the phototoxic effect of these compounds.     

PHOTOCHEMISTRY OF HEPARIN-ACRIDINE ORANGE COMPLEXES IN SOLUTION: PHOTOCHEMICAL CHANGES OCCURRING IN THE DYE AND POLYMER ON FLUORESCENCE FADING

Abstract— Photolysis of acridine-orange-heparin complexes in N₂- and O₂-saturated solution results in permanent photooxidation of AO with little or no concomitant change in the heparin moiety. The major photoproduct is mono- N -demethylated acridine orange; in O₂-saturated solution an additional minor oxygenated product, most likely the 10-oxide (N-oxide) or the 9-acridanone (acridone) is also formed. The results suggest an intermolecular electron transfer between adjacently adsorbed dye molecules. The heparin moiety plays a significant role in the photochemistry by bringing dye molecules into favorable geometric orientation for biomolecular reaction and by means of specific dye-polymer interactions.     

杂环光化学——Ⅲ. 核酸碱基衍生物的电子光谱研究

测定了脲嘧啶、胸腺嘧啶、6-氮杂脲嘧啶、6-氮杂胸腺嘧啶和它们的相应的二甲基衍生物以及鸟嘌呤、8-氮杂鸟嘌呤等十个化合物的吸收光谱、荧光光谱和磷光光谱。讨论了这类化合物的分子结构与光物理过程及激发态之间的关系。     

PHOTOBIOLOGICAL PROPERTIES OF A NOVEL, NATURALLY OCCURRING FUROISOCOUMARIN, CORIANDRIN

The photobiological properties of a novel, naturally occurring furoisocoumarin isolated from coriander and named coriandrin are described. Photosensitized lethal and mutagenic effects in bacteria indicate that it is more active than psoralen. It is a weak frameshift mutagen in the dark. Mammalian cells in tissue culture are photosensitized more actively with coriandrin than with psoralen even though preliminary evidence from interrupted radiation experiments and DNA analysis suggest that coriandrin does not form DNA interstrand crosslinks. Sister chromatid exchanges were induced with a unit dose of 1.1 x 10(-2) with coriandrin; the value for psoralen is 3 x 10(-3). Coriandrin appears to be metabolized more rapidly than furocoumarins by liver mixed function oxidases. Skin photosensitizing activity is very weak compared with psoralen, a surprising observation considering its potency in biological test systems.     

THEORETICAL CALCULATIONS OF THE TRANSITIONS OF PHOTOCOLORED FORMS OF CHROMENES

Abstract— –Theoretical prediction (MO-SCF-CI) of numbers, energies and intensities of transitions are compared with experimental data for the photocolored products of three types of chromenes. Generally good results are obtained. Several conclusions resulted from variation of parameters: (1) When all carbon-carbon bonds are considered equal in length, there is good agreement between experiment and theory regarding band locations and intensities, however, very poor correlation exists between theory and experiment when calculations are done on a model where the carbon-carbon bonds are alternately single and double, (2) theoretical calculations employing the Mataga approximation for the two-center repulsion integrals gives superior correlation with the experimental spectra in comparison with the Pariser-Parr approximation, and (3) variation of certain parameters (as I.P., E.A., β) did produce changes in the results, especially in the oscillator strengths, but there was no clear best choice, and therefore, conventional parameters were used.     

THE PHOTOCHEMISTRY AND CRYSTAL STRUCTURE OF SOLID 1-CHLOROANTHRACENE

Abstract— Although the blue-fluorescent (type A) crystalline modification of lthloro-anthracene is photochemically stable, the green-fluorescent modification (type B) undergoes photodimerisation on exposure to the Hg line at 365 mμ, to produce a different solid modification of the dimer from that precipitated from an exposed soIution.     

THE INFLUENCE OF FLAVONOID SULFONATES ON THE FLUORESCENCE AND PHOTOCHEMISTRY OF FLAVYLIUM CATIONS

Abstract— The effects of flavone sulfonic acid 9 andquercetin–5'-sulfonic acid 10 on the luminescence spectra of eight flavylium salts have been determined. The non-hydroxylated flavone 9 was found to enhance the luminescence of those flavylium salts, while the polyhydroxyflavonol 10 was shown to exert the opposite effect. These findings are rationalized in conjunction with prior observations on the enhancement and inhibition of the photodecomposition of anthocyanins exerted by 9 and 10 , respectively.     

PHOTOPHYSICS AND PHOTOCHEMISTRY OF PHOTOREACTIVATION

Abstract— Photoreactivating enzyme (PRE) monomerizes cyclobutyl pyrimidine dimers formed in DNA by UV light ( Λ < 300 nm). The enzyme requires near UV and visible wavelengths (300 < Λ < 600 nm) for activity. Possible mechanisms of action of the PRE are suggested by non-enzymatic processes in which pyrimidine dimers are monomerized by UV and visible light. Two such non-enzymatic processes are (a) photolysis of dimers resulting from direct absorption of UV, and (b) sensitized monomerization involving charge transfer complexes. Several lines of evidence suggest that the mechanism of action of the PRE more closely resembles (b) than (a). Recent experiments on the PRE from E. coli reveal the presence of new long wavelength absorption which may indicate the presence of a ground state complex. The known ability of PRE to monomerize dimers of thymine, cytosine and uracil suggests that the carbonyl groups at 2 position of the pyrimidine ring may be important in the interaction between enzyme and dimer.