THE FORMATION OF HYDRATED ELECTRONS FROM THE EXCITED STATE OF INDOLE DERIVATIVES

Abstract— –Hydrogen atoms can be observed in u.v. irradiated aqueous solutions of indole derivatives. These H' atoms are produced in a reaction between H⁺ and solvated electrons which are formed in the excited state of indole. Protons are also known to be good quenching agents for the fluorescence of indole. However the pH dependence and effect of oxygen on the yield of hydrogen atoms indicates clearly that although both fluorescence and electron ejection originate in the excited singlet state the fluorescence quenching by protons is not caused by a transfer of electronic charge from the excited ring to H⁺. The temperature dependencies of both fluorescence and electron ejection yield an abnormally large "activation energy". It is proposed that this temperature dependence is to a large extent determined by a process characteristic of water as a solvent.     

PHOTOCHEMICAL FORMATION OF NITROXIDE RADICALS FROM CARCINOGENIC N-METHYL-N'-NITRO-N-NITROSOGUANIDINE AND RELATED COMPOUNDS

Abstract— Potent carcinogenic N -methyl- N '-nitro- N -nitrosoguanidine (MNNG) was found to be converted into a free radical by photoirradiation in organic solvents. The structure of the free radical produced was investigated by means of the electron paramagnetic resonance (EPR) method using isotope-replaced compounds and also considering the results of the molecular orbital calculations. Upon illumination, release of the nitroso group and oxygen attack at the N -methyl nitrogen occurred, and the radical was identified as a nitroxide radical. Similar types of nitroxide radical were obtained from other N -alkyl- N -nitroso compounds, such as N -ethyl-, N -propyl-, and N -butyl- N '-nitro- N -nitroso-guanidine.     

IMINOSULFURANES FROM BIOLOGICALLY ACTIVE SULFONAMIDES AND RELATED COMPOUNDS

Abstract

Iminosulfuranes and iminosulfonium salts have been prepared from biologically active sulfonamides and other biologically active and related amino compounds. The new compounds have been characterized by nmr, uv, ir, mass spectra and elemental analysis. Deuterated analogs have also been prepared in selected cases for mass spectral comparison with their nondeuterated counterparts.     

氨基硫脲及其相关化合物的化学

本文综述了氨基硫脲及其相关化合的合成、波谱和化学性质以及在药物、工业、农业等方面的应用。     

TELLUROLOTHIOPHENE AND RELATED COMPOUNDS

Abstract

Unsubstituted 2-thienyllithium reacts successively with elemental tellurium and alkylhalides giving rise to 2-alkyltellurothiophenes.     

PAIRWISE RECOMBINATION IN THE DECAY OF PHOTOCHEMICAL HYDRATED ELECTRONS*

Abstract— The decays of hydrated electrons generated by 265 nm laser flash photolysis of aqueous I^-, tyrosine, tryptophan, lysozyrne. and ribonuclease have been analyzed by numerical computing. Homogeneous reactions do not explain the data without e^- _aq—radical back reactions significantly faster than diffusion limited. The results are explained by postulating pairwise recombination persists at times where conventional diffusion theory predicts randomization, particularly at low intensities and in the absence of effective e^- _aq scavengers. The physical mechanisms responsible for these effects are considered.     

ABSORPTION SPECTRA AND PPP-MO CALCULATIONS OF THIOPYRAN AND RELATED COMPOUNDS

Abstract

The absorption bands of the coumarin, the thiocoumarin and thiochromone have been examined by the PPP calculation with variable β approximation, changing with increasing ring size. The calculated longest-wavelengths (λ₁) of these series were in good agreement with the experimental values measured in ethanol. A bathochromic displacement of λ₁ produced by annelation of a benzene ring to a 2H-pyran-2-one, a coumarin and its thio analogues might be mainly due to a reduction of LUMO energy levels and/or increase of HOMO energy levels. The substituent effect on absorption spectra in the coumarin, the thiocoumarin and thiochromone series has also been examined, and discussed in terms of PPP calculations.     

CHOLESTERYL PHOSPHITE AND RELATED COMPOUNDS

Abstract

The preparation of cholesteryl phosphorodichloridite (2) is described; this compound with aniline (2 mol. equiv.) gave the N-phenylphosphoramidochloridite (5) and the latter by condensation with water afforded the N-phenyl-amidophosphite (6).

Similarly the N-phenylphosphoramidochloridite (5) with morpholine gave the morpholidite (7); phenylhydrazine gave the hydrazinophosphite (8) and ethanol the amidoethyl phosphite (9). Cholesteryl phosphorodichloridite (2) by reaction with aniline (4 mol. equiv.) gave the N,N ¹?diphenylphosphorodiamidite (10).

The reaction of cholesteryl phosphorodichloridite (2) with methanol and ethanol are discussed in relation to the analogous reactions with cholesteryl phosphorodichloridate. Boiling ethanol gave cholesterol as the only isolatable product but at room temperature a low yield of the diethylphosphite (11; R=Et) was obtained. The yield of the phosphite was greatly increased in the presence of base. Similarly the dichloridite 2 with boiling water gave cholesterol (1), but at room temperature cholesteryl phosphite 3 was isolated: the mechanistic basis for these different results is briefly discussed.

trans-4-t-Butylcyclohexanol with phosphorus trichloride gave the phosphorodichloridite, which was characterised by conversion to the corresponding N,N ¹?diphenylphosphorodiamidite.     

MOLECULAR AMD CRYSTAL STRUCTURES OF LIPIDS AND RELATED COMPOUNDS

Molecular-level structures of lipids and related organic long-chain compounds were investigated by means of vibrational spectroscopic and X-ray diffraction methods. Various spectroscopic techniques applicable to structural studies of lipid systems were developed. Various types of solid-state phase transformations were found in even- and odd-numbered saturated fatty acids and their molecular mechanisms were considered. Crystal structures of some modifications of a series of cis-mono-unsaturated fatty acids were determined by the three-dimensional X-ray analysis and new types of molecular conformation as well as of subcell arrangement of the cis-mono-unsaturated acyl chains were found. An order-disorder type phase transformation accompanied with a partial melting at the interface of the molecular layers was found in some modifications of cis-mono-unsaturated fatty acids. Molecular conformations and crystal structures of the polymorphs of methyl oleate and triglycerides containing an oleoyl chain at the 2-position were investigated on the basis of the spectroscopic data.     

ON THE PHOTOSENSITIZING PROPERTIES OF N-FORMYLKYNURENINE AND RELATED COMPOUNDS

Abstract— The photochemical and photosensitizing properties of N -formylkynurenine (FK) and related compounds have been investigated using the laser flash photolysis technique by exciting water solutions with 265 nm or 353 nm radiation. The FK molecules in their first excited singlet state readily react with water leading probably to OH formation. FK triplet state reacts with many biological compounds including vitamins, amino acids and nucleic acid bases. The semi-reduced FK thus formed can, in turn, reduce substrates such as cytochrome c or O₂.     

ELECTRON TRANSFER FROM THE EXCITED STATE OF TYROSINE TO COMPOUNDS CONTAINING DISULFIDE LINKAGES

Abstract— The flash photolysis of aqueous solutions of tyrosine has been studied in the presence of various concentrations of the cyclic disulfide sodium lipoate (thioctic acid, Na⁺ salt). In addition to the formation of phenoxyl radicals and hydrated electrons (and possibly H atoms) from the photoionization of tyrosine, the characteristic spectrum of the radical anion RSSR^- of lipoate was also observed in neutral as well as in alkaline solutions. From the dependence of these yields upon the concentration of lipoate, it was found that a long–lived triplet excited state of tyrosine, rather than the singlet excited state, is involved in these reactions. The negative radical ions RSSR^- are formed by two distinct pathways: (a) Na⁺–lipoate reacts with the solvated electrons which are ejected from the tyrosine triplets ³Tyr → RO.+ e ^-_aq+ H⁺ followed by e ^-_aq+ RSSR → RSSR^-, and (b) by direct interaction of lipoate with triplet excited tyrosine, resulting in the transfer of a negative charge from tyrosine to the disulfide linkage. At high lipoate concentrations, the singlet excited state of lipoate is quenched, k ₄= 1.6 × 10¹⁰ M ^-1 sec^-1, but this reaction does not lead to the formation of RSSR^- radical ions.     

THE MASS SPECTRAL FRAGMENTATION OF SULFENAMIDES AND RELATED COMPOUNDS

Abstract

Plausible mechanistic interpretations of the major ions formed in the mass spectrometric fragmentation of a number of sulfenamides and related derivatives are presented. High resolution mass spectrometry was used to determine the composition of most of the ions investigated.     

THE EFFECT OF AROMATIC AMINO ACIDS ON THE PHOTOCHEMISTRY OF A DISULFIDE: ENERGY TRANSFER AND REACTION WITH HYDRATED ELECTRONS

Abstract —The decomposition of dithioglycolic acid in oxygen-free solutions illuminated by low-intensity 254 nm light at pH 1.5-4.7 is enhanced by light absorbed in tyrosine. This occurs through an interaction with excited tyrosine, leading to the formation of excited dithioglycolic acid. At pH 6-1 an additional pathway appears, through the formation of a hydrated electron from excited tyrosine.
In the presence of tryptophan at pH 1 -2–6-1 the pathway involving sensitized formation of excited dithioglycolic acid is much less important, and that due to hydrated-electron (or H ) formation from excited tryptophan of greater importance.     

DIRECT DETECTION OF SINGLET OXYGEN SENSITIZED BY HAEMATOPORPHYRIN AND RELATED COMPOUNDS

Abstract— Direct time-resolved detection of the luminescence at 1270 nm from 'singlet oxygen' was used to estimate the quantum yield of singlet oxygen production (Φ_Δ) from a series of related porphyrins in benzene and in D₂O. From this and available data the fraction of oxygen quenching interactions leading to singlet oxygen production (S_Δ) was derived in most cases. A marked increase in Φ_Δ value was observed for di-haematoporphyrin ester (DHE) in cetyltrimethyl ammonium bromide/D₂O solution in comparison to D₂O alone, this increase is attributed to a major structural alteration of DHE on introduction of the detergent.     

PREBIOTIC FORMATION OF HIGHER MOLECULAR WEIGHT COMPOUNDS FROM THE PHOTOLYSIS OF AQUEOUS ACETIC ACID

In the study of chemical evolution, experiments simulating primitive earth conditions have shown that many compounds of biological significance can be produced from simple precursors. In an attempt to search for the origin of polycarboxylic acids, the UV irradiation of aqueous acetic acid was performed. Among the products detected were succinic, citric and malonic acids which are key compounds in metabolic pathways, suggesting that these compounds might have been formed on the primitive Earth prior to life itself.     

FLUORESCENCE QUENCHING OF INDOLIC COMPOUNDS BY ALIPHATIC AMINO ACIDS. EVIDENCE FOR EXCITED STATE COMPLEXES

Abstract The fluorescence quenching of indole, tryptophan, tryptamine and indole-3-acetic by aliphatic amino acids was studied. The bimolecular rate constant ( k _q) for the deactivation of the excited state was determined. The k _q values were in the range 0.6 × 10⁸–1.6 × 10⁹ M ^–1 S^–1 and they increased in the order tryptophan < tryptamine < indole ≈ indole-3-acetic acid. When the rate constant was corrected for diffusion al effects a good linear correlation was found between the log ( k '_q) and the ionization equilibrium constant of the carboxylic group of the amino acid (p ^k _a1). This was interpreted as arising from a charge transfer mechanism in which the indole moiety acts as an electron donor and the carbonyl group of the amino acid as the acceptor.
The activation parameter for the quenching processes were also determined. The ΔH^≠ values were in the range —4.0 to +4.0 kcal/mol and the ΔH^≠ in the range –7 to –37 e.u. For the systems with lower values of k _q negative values for ΔH^≠ were observed. A good enthalpy-entropy compensation was found with an isokinetic temperature of 229 K. These results suggest that a common mechanism is operating for all the systems and that it involves the formation of an excited state complex between the indolic compound and the amino acid.     

基团电负性与含氧有机物的标准生成热

本文利用作者提出的基团电负性,建立了一个计算含氧有机物标准生成热的简单方法: △fH°(RZ)=△fH°(CH_3Z)-(0.48 n~(1/2)+17.18)x_G-20.13n+69.71式中,△fH°(RZ)和△fH°(CH_3Z)分别为含氧有机物RZ和CH_3Z的标准生成热;Z-OE_e、OM_e、OH、COCH_3、CHO、CO_2H、CO_2Me、CO_2Et.CONH_2;x_G为基团Z的电负性;n是直链烷基R中的碳原子个数,48个可比较值的平均偏差为0.3kCal/mol。     

MULTIPLE PATHWAYS IN THE BASE-CATALYZED REACTIONS OF S-ALLYL SULFONIUM COMPOUNDS

Abstract

Various S-allyl sulfonium salts were allowed to react with bases (EtONa/EtOH, NaH/THF). From product analyses, it was found that modes of reaction depend on both the structure of sulfonium salts and the bases employed. Among the observations, it is worthy to note the formation of cyclopropane derivatives from some allyl sulfonium salts.     

SOME HETEROCYCLIC PHOSPHOROCHLORIDATES AND THE FORMATION OF OTHER HETEROCYCLIC ORGANOPHOSPHORUS COMPOUNDS

Abstract

Pyrrolidine, morpholine, and β-hydroxyethylmorpholine have been phosphorylated with phosphorus oxychloride, phenylphosphorodichloridate, p-chlorophenylphosphorodichloridate and thiophosphoryl chloride. The resultant phosphorodichloridates have been condensed with a wied range of nucleophilic reagents, e.g. amines, hydrazines, phenols and isobutanol. Piperazine with phosphorus oxychloride (2 mols) gave the N(1) N(4)-diphosphorotetrachloridate, which was characterized as the tetracyclohexylamidate. β-Hydroxyethylpiperazine was similarly phosphorylated to the N,O-diphosphorotetrachloridate which was characterized as the tetraphenylhydrazidate.

Condensation of pyrrolidine (2 mols) with phosphorus oxychloride (1 mol) afforded N,N′-dipyrrolidinophosphorochloridate which was reacted with phenylhydrazide and sodium azide. The phosphoroazide with triphenylphosphine afforded the corresponding triphenylphosphinimine. N-Phenyl N′-pyrrolidinophosphorochloridate with aqueous pyridine gave the corresponding pyrophosphoramide and the stability of the pyrophosphoramide towards hydrolysis was examined. 1,2-Cyclohexanediol was phosphorylated with phenylphosphorodichloridate and thiophosphorylchloride. Trans-4-t-Butylcyclohexyl N,N′-diphenylhydrazinophosphorothioate by reaction with formaldehyde gave a tetra-azaphosphorine P-sulfide. Trans-4-t-Butylcyclohexyl N-phenyl N′-phenylphosphorodiamidic hydrazide reacted with 1,4-dibromobut-2-ene to give a 1,2-diazahex-4-ene.