SPECTROSCOPIC PROPERTIES OF PSORALEN DERIVATIVES SUBSTITUTED BY CARBETHOXY GROUPS AT THE 3,4 AND/OR 4,5' REACTION SITE

Abstract— The newly synthesized linear psoralen derivative 3-carbethoxypsoralen has been shown recently to behave as a monofunctional derivative and has attracted some interest in the psoriasis treatment. In a first attempt to understand, by the fluorescence technique, the molecular mechanism by which it interacts with DNA, a spectroscopic study of the molecule was undertaken. The fluorescence of 3-carbethoxypsoralen at room temperature resembles that of 8-methoxypsoralen with a ten times higher quantum yield. 365 nm irradiation of dilute solutions of 3-carbethoxypsoralen rapidly leads to the formation of two types of highly fluorescent photoproducts. Type 1 photoproducts (λ_em^max= 425 nm, λ_exc^max= 360 nm) have been identified as the result of the addition of a solvent molecule to the 4,5' reaction site of the molecule. Their fluorescence intensity is a hundred times higher for 3-carbethoxypsoralen than for 8-methoxypsoralen. They become negligible when the 4',5' reaction site carries also a carbethoxy group. Type 2 photoproducts exhibit a somewhat different emission (λ_em^{max =} 443 nm, λ_exc^max= 413 nm). They are probably the result of an opening of the furocoumarin molecule. The implications of the peculiar photochemical properties of 3-carbethoxypsoralen are discussed in view of its biological activity. In addition, the use of fluorescence in monitoring the photobinding of psoralens to DNA is also discussed     

THE PHOTOBIOLOGICAL ACTIVITY OF 5-GERANOXYPSORALEN AND ITS PHOTOPRODUCTS

5-geranoxypsoralen (Bergamottin) does not photosensitize bacteria or a bacterial virus. It does, however, photosensitize mammalian cells in tissue culture. Irradiation with either black light (300-400 nm) or fluorescent ceiling lights produced at least four photobiologically active degradation products, the chemical nature of which still remains to be elucidated. Prolonged exposure to black light resulted in the formation of inactive molecule(s).     

C4-CYCLODIMERS OF PSORALEN ENGAGING THE 4'',5''- DOUBLE BOND

Abstract— By irradiating psoralen (the parent linear furocoumarin) in thin solid film two new fluorescent photodimers. compounds I and II, have been isolated and characterized. Unlike previously isolated dimers of furocoumarins which showed a 'pyrone-pyrone' structure involving in the C₄-cycloaddition the 3,4-double bond of the furocoumarinic moiety, the new dimers show respectively a 'furan-furan' and a 'furan-pyrone' structure, involving therefore the 4',5'-double bond. By analogy with the photocycloaddition reactions between furocoumarins and pyrimidine bases of DNA, in this case too the 4',5'-double bond of the furocoumarin can be involved. The experimental conditions, however, in which irradiation is carried out play an important role.     

4, 4'', 5''-TRIMETHYL-8-AZAPSORALEN, A NEW-PHOTOREACTIVE AND NON-SKIN-PHOTOTOXIC BIFUNCTIONAL BIOISOSTER OF PSORALEN

Photochemical and photobiological properties of a new isoster of psoralen, 4,4',5'-trimethyl-8-azapsoralen (4,4',5'-TMAP), have been studied. This compound shows a high DNA-photobinding rate, higher than that of 8-methoxypsoralen (8-MOP), forming both monoadducts and inter-strand cross-links. The yield of cross-links, however, is markedly lower than that of 8-MOP. Antiproliferative activity of 4,4',5'-TMAP, in terms of DNA synthesis inhibition in Ehrlich ascites tumor cells, is higher than that of 8-MOP. Mutagenic activity on E. coli WP2 R46+ cells appeared similar to or even lower than that of 8-MOP. This new compound applied on depilated guinea pig skin and irradiated with UVA did not show any skin-phototoxicity. On the basis of these properties 4,4',5'-TMAP appears to be a potential photochemotherapeutic agent.     

CORRELATION BETWEEN THE TRIPLET PHOTOPHYSICAL PROPERTIES AND THE PHOTOBIOLOGICAL ACTION IN YEAST OF TWO MONOFUNCTIONAL PYRIDOPSORALENS

The photophysical properties of the lowest excited triplet states of pyrido[3,4-c]psoralen (PyPs) and 7-methylpyrido[3,4-c]psoralen (MePyPs) have been investigated by laser flash photolysis, including energy transfer from these triplets to oxygen-generating singlet oxygen. A parallel study of the photosensitization of yeast in vivo by these compounds in the presence and absence of oxygen is also reported. The low triplet and hence singlet oxygen yields, reflected in the lack of an oxygen effect in yeast, suggest that photoadditions to DNA are likely to be the main source of the photosensitized lethal effects induced by these pyridopsoralens in vivo.     

3,4 AND 4'',5''-PHOTOCYCLOADDUCTS BETWEEN 4''-METHYLANGELICIN AND THYMINE FROM DNA

Abstract— Two C₄-cycloadducts between 4'-methylangelicin and thymine were isolated from the photo-reaction (365 nm) between this furocoumarin and DNA. Their capacity to undergo photoreversion at 254 nm and their spectroscopic and NMR data allowed us to assign furan- and pyrone-side structures, respectively, to these photocompounds. The former adduct has a cis-syn configuration; the latter. which was also isolated from a photoreaction between the furocoumarin and thymine in water-methanol solution, was assigned a cis-anti structure.     

METHYLALLOPSORALEN-THYMINE 3,4- and 4'',5''-MONOADDUCTS FORMED IN THE PHOTOREACTION WITH DNA

Abstract— Two new allopsoralens, i.e. 4,7.5'-trimethylallopsoralen and 4,7,4'-trimethylallopsoralen have been irradiated (365 nm) in the presence of DNA. The DNA so treated was hydrolyzed and among the products of its hydrolysis new 3,4- and 4',5'-monocycloadducts between the two furocoumarins and thymine have been isolated. The monoadducts have been characterized on the basis of their spectroscopic properties, of their capacity to undergo photoreversion forming the parent compounds and of the NMR data. A cis-syn conformation has been suggested for both 3,4- and both 4',5'-monoadducts.     

A NOVEL METHOD FOR THE PREPARATION OF SUBSTITUTED 5-AMINO-1,2,3, 4-THIATRIAZOLES BY AZA-TRANSFER REACTION

Abstract

Recently, the aza-transfer reactions between amino or hydrazino compounds and aryldiazonium salts or heterocyclic diazo compounds have been studied. In general, a mixture of different products is formed.     

THE SYNTHESIS OF SOME C-4 AND C-9 SUBSTITUTED DERIVATIVES OF KDN2EN METHYL ESTER

The synthesis of a number of C-4 and C-9 substituted derivatives of KDN2en methyl ester 2 is reported. 9-Deoxy-9-iodo, 9-azido-9-deoxy and 9-O-methyl derivatives of 2(compounds 5, 7and 9) were prepared from the corresponding 9-O-tosylate, methyl 2,6-anhydro-3-deoxy-9-O-p-toluenesulfonyl-D-glycero-D-galacto-non-2-enonate (3). These compounds have been fully characterised as the peracetates 6, 8 and 10. Treatment of 3 with KSAc gave the 9-thioacetyl derivative which was isolated as the peracetate 11. 4-C-Ethenyl-4-deoxy (14), 4-C-phenyl-4-deoxy (15) and 4-C-[1-(methoxycarbonyl)ethenyl]-4-deoxy (16) derivatives of 2were prepared via the palladium-catalysed coupling of the 4-epi-chloride, methyl 5,7,8,9-tetra-O-acetyl-2,6-anhydro-4-chloro-3,4-dideoxy-D-glycero-D-talo-non-2-enonate (12) with the appropriate organostannanes.     

PHOTOBIOLOGICAL ACTIVITY OF MARMESIN (5-B-HYDROXYISOPROPYL-4–5 DIHYDROFUROCOUMARIN) IN CHINESE HAMSTER V79 CELLS

Abstract— Marmesin was isolated from the medicinal plant, Afraegle paniculata. Its cytotoxicity and mutagenicity in Chinese hamster V79 cells when sensitized to near ultraviolet (NUV) and long wavelength ultraviolet light or black light (BL) were assayed.
Marmesin was extremely cytotoxic in the dark. This cytotoxicity was photoenhanced in NUV and BL; the photoenhanced lethality being higher in NUV than in BL. The LD₅₀ of marmesin under NUV and BL photosensitization were 0.002 μ M and (0.012 μ M ), respectively. In the absence of NUV and BL, marmesin's LD₅₀ was 0.013 μ M . NUV and BL without marmesin were not significantly cytotoxic at the fluence rates of 0.29 W/m² and 4.2 W/m², respectively, for up to 20 min. In contrast to the observed high cytotoxicity of marmesin, its mutagenicity at the HGPRT locus (A_zG^r) was weak. The implication of this result in the high incidence of skin cancer in Nigeria in which A. paniculata is used as a medicinal plant is discussed.     

TRIPLET EXCITED STATE OF THE 4'5' PHOTOADDUCT OF PSORALEN AND THYMINE

Abstract— The triplet-triplet absorption spectrum of the 4'5' psoralen-thymine mono-adduct has been determined in water and methanol using the technique of laser flash photolysis. The extinction coefficient of the triplet was measured by the energy-transfer method with retinol triplet as standard, and used to determine the singlet → triplet intersystem crossing quantum yield for 353 nm excitation. Reaction rate constants for mono-adduct triplet with thymine and tryptophan were measured in water. Long-lived transient absorptions detected after quenching the mono-adduct triplet with thymine and tryptophan are assigned mainly to the corresponding mono-adduct radical anion, whose spectrum was established in separate pulse radiolysis studies of the mono-adduct in aqueous formate.
The significant singlet → triplet quantum yields found for the mono-adduct might be consistent with the involvement of triplet excited mono-adduct in DNA cross-link formation, as also may be the high reactivity obtained for the triplet with thymine. The initial quenching products observed resulted from a charge-transfer reaction.     

A SURVEY OF IN VIVO PHOTODYNAMIC ACTIVITY OF XANTHENES, THIAZINES, AND ACRIDINES IN YEAST CELLS

Abstract. In view of the recent interest in the possibility of a singlet oxygen mechanism playing an important role in photodynamic action, a number of different types of dyes were surveyed with respect to cell inactivation and induction of genetic changes in yeast cells. These comprise three xanthene dyes, three thiazine dyes, three acridine dyes and ethidium bromide. Rhodamine B in the first group and methylene blue in the second group were inactive under the present conditions. Both were found to be non-penetrable into the cell. However, since toluidine blue is active, non-penetrability is not a determining factor in photodynamic action. Ethidium bromide was inactive under the present conditions, even though it was penetrable into the cell. The survey showed that the dye must be bound to DNA in order to be active in the induction of a genetic change (gene conversion). All dyes which were active in either inactivation or induction or both were modified in their effectiveness both by the addition of N^-₃ (suppression) and in deuterated medium (enhancement), indicating that the sensitization mechanism involves singlet oxygen. The deuterium effect was generally observable to a lesser extent in the in vivo situation than in vitro , in particular for genetic changes by profiavine and acriflavine in which the sensitizer binds to DNA.     

EFFECT OF MOLECULAR STRUCTURE ON THE PHOTOPHYSICAL PROPERTIES, THE PHOTOREACTIVITY WITH DNA AND THE PHOTOBIOLOGICAL ACTIVITY OF MONOFUNCTIONAL PYRIDOPSORALENS

Abstract— 7-Methyl-pyrido[4,3-c]psoralen (2N-MePyPs) has been synthesized in order to investigate the possible effect of the position of the pyridine-nitrogen atom on the photoreactivity towards DNA and the photobiological activity of pyridopsoralens, a new family of psoralen derivatives. In comparison to its isomer, 7-methyl-pyrido[3,4-c]psoralen (MePyPs), 2N-MePyPs shows a 2.5 times lower DNA photobinding capacity. Photobiological experiments with diploid yeast ( Saccharomyces cerevisiae ) reveal that this compound differs strikingly from its isomer MePyPs. It has only a weak antiproliferative potential and, per unit dose, a lower capacity than MePyPs for the induction of nuclear genotoxic effects. With respect to these latter features, 2N-MePyPs resembles the monofunctional furocoumarin 3-CPs.     

硫酸铜催化下乙烯酮、乙酐与环酮、戊二酮及乙酰乙酸乙酯的反应

烯醇酯是合成高分子化合物的单体,较早由快烃与羧酸反应得到,1944年Bedoukian用醋酸钾为催化剂由异丁醛与乙酐反应得到乙酸异丁烯酯,Gwynn等在硫酸、磷酸等催化下由乙烯酮与酮反应合成了乙酸烯醇酯。我们曾由环戊酮、环己酮在硫酸铁催化下合成了环烯醇酯。本文在合成反应中改用硫酸铜为催化剂时提高了烯醇酯的产率。     

天然萜类分子中部分共轭五员环的内应力与抗肿瘤活性

本文讨论了某些香茶菜属植物中的贝壳杉烯(ent-Kaurene)及 B-闭联贝壳杉烯(B-Seco-Kaurene)等化合物中的α-亚甲基环戊酮、α-亚甲基五员内酯环、α-亚甲基六员内酯环以及含有两个sp~2杂化碳原子的五员环等结构,由于它们具有一定的内应力而导致化合物的化学活性提高,它可能与抗肿瘤活性之间有一定关系。     

THE INVOLVEMENT OF WATER AT THE RETINAL BINDING SITE IN RHODOPSIN AND EARLY LIGHT-INDUCED INTRAMOLECULAR PROTON TRANSFER

Abstract Extensive dehydration of air-dried films of bovine rod outer segment membranes induces fully reversible changes in the absorption spectrum of rhodopsin, indicative of deprotonation of the retinylidene Schiff base in more than 50% of the rhodopsin molecules in the sample. This suggests that water is involved at the site of the Schiff base protonation in rhodopsin. In contrast, the spectrum of metarhodopsin I is resistant to similar dehydrating conditions, implying a significant difference in the mechanism for protonation in metarhodopsin I. The photochemistry of dehydrated membranes was also explored. Photoexcitation of deprotonated rhodopsin (λ_max 390 nm) induces a large bathochromic shift of the chromophore. The major photoproduct at room temperature was spectrally similar to metarhodopsin I (λ_max, 478 nm). These findings suggest that intramolecular proton transfer involving the Schiff base proton may occur in the earlier stages of the visual cycle, prior to or during the formation of metarhodopsin I.     

低温条件下二氧化碳存在时羰基硫催化水解本征动力学

在自行设计和安装的一套微反-色谱联用装置上，以TGH为催化剂，进行了二氧化碳对羰基硫催化水解本征动力学影响的研究，得出了在低温50 ℃～70 ℃、高水汽摩尔比(H2O/COS=60～550)，分别对原料气中有无存在CO2的条件下,采用非线性Marquart法对实验数据进行回归，所建立的本征动力学方程式为：     

Zn-CCl2F2-H2O体系的低温基质隔离化学反应

低温基质隔离技术与各种光谱技术相结合,作为研究活性分子、分子结构、催化、光化学和制备新物质的一种重要方法,在国外已相当普遍,特别是在无机低温制备方面,由于涉及金属原子的低温化学反应具有简单性和自发性两大优点,近十多年来已有很大发展,专家们预言,低温无机合成化学,二十年后将成为一种重要的合成方法.目前国内尚未见有报道,本文介绍我们在这方面的初步尝试.