Chiral recognition between lactic acid derivatives and an aromatic alcohol in a supersonic expansion: electronic and vibrational spectroscopy

Jet-cooled diastereoisomeric complexes formed between a chiral probe, (+/-)-2-naphthyl-1-ethanol, and chiral lactic acid derivatives have been characterised by laser-induced fluorescence and IR fluorescence-dip spectroscopy. Complexes with non chiral alpha-hydroxyesters and chiral beta-hydroxyesters have also been studied for the sake of comparison. DFT calculations have been performed to assist in the analysis of the vibrational spectra and the determination of the structures. The observed 1 : 1 complexes correspond to the addition of the hydroxy group of the chromophore on the oxygen atom of the hydroxy in alpha-position relative to the ester function. Moreover, (+/-)-methyl lactate and (+/-)-ethyl lactate complexes with (+/-)-2-naphthyl-1-ethanol show an enantioselectivity in the size of the formed adducts: while fluorescent 1 : 1 complexes are the most abundant species observed when mixing (S)-2-naphthyl-1-ethanol with (R)-methyl or ethyl lactate, they are absent in the case of the SS mixture, which only shows 1 : 2 adducts. This property has been related to steric hindrance brought by the methyl group on the hydroxy-bearing carbon atom.     

Spectrophotometric study on the adduct formation of nickel (II)-di(2,4-dimethylphenyl)carbazonate with heterocyclic nitrogen bases

The study of the adduct formation of Ni(II)di(2,4-dimethylphenyl)cabazonate has been undertaken by synthesising and characterising it by magnetic susceptibility, IR and 1H-NMR spectral measurements. The Ni(II) chelate forms adducts with heterocyclic nitrogen bases, spectrophotometeric method has been employed for the study of the adduct formation in a monophase chloroform. Both bidentate and unsaturated monodenate heteronuclear nitrogen bases form hexa-coordinated adducts with 1:1 stoichiomety (metal chelate, base). However, the saturated nitrogen bases form penta-coordinated adducts with 1:1 stoichiometry. The results are discussed in terms of basicity and steric factors of the bases.     

A study of adduct formation of heterocyclic nitrogen bases with nickel(II) chelate of di(6-chloro-2-methylphenyl)carbazone

The study of the adduct formation of Ni(II) di(6-chloro,2-methylphenyl)carbazonate has been undertaken by synthesising and characterizing it by magnetic susceptibility, UV-VIS, IR and 1H-NMR spectral measurements. The distorted square planar Ni(II) chelate forms adducts with heterocyclic nitrogen bases; spectrophotometric method has been employed for the study of the adduct formation in a monophase chloroform. Both bidentate and unsaturated monodentate heteronuclear nitrogen bases form hexacoordinated adducts with 1:1 and 1:2 stoichiometry, respectively (metalchelate:base). However, the saturated nitrogen bases form pentacoordinated adducts with 1:1 stoichiometry. The results are discussed in terms of basicity and steric factors of the bases.     

Structural and photophysical characterization of multichromophoric pyridylporphyrin-rhenium(i) conjugates

Four porphyrin-Re(I) conjugates, in which a pyridylporphyrin chromophore is directly coordinated to the electron-acceptor fragment [ fac-Re(CO) 3(bipy)] (+), were prepared: the dimeric and pentameric compounds [ fac-Re(CO) 3(bipy)(4'MPyP)](CF 3SO 3) ( 1) (4'MPyP = 4'-monopyridylporphyrin) and [ fac-{Re(CO) 3(bipy)} 4(mu-4'TPyP)](CF 3SO 3) 4 ( 2) (4'TPyP = 4'-tetrapyridylporphyrin), and the corresponding compounds with 3' rather than 4' porphyrins, [ fac-Re(CO) 3(bipy)(3'MPyP)](CF 3SO 3) ( 3) and [ fac-{Re(CO) 3(bipy)} 4(mu-3'TPyP)](CF 3SO 3) 4 ( 4). These adducts proved to be very stable in solution and were also structurally characterized in the solid state by X-ray crystallography. A detailed photophysical study was performed on the zincated adducts of the conjugates 1- 3, labeled 5, 6, and 7, respectively. In all adducts the typical fluorescence of the zinc-porphyrin unit was reduced in intensity and lifetime by the presence of the peripheral rhenium-bipy fragment(s) (heavy-atom effect). For the dyads 5 and 7 the photoinduced charge transfer process from the zinc-porphyrin to the Re(I)-bipy unit is only slightly exoergonic. Ultrafast spectroscopy experiments showed no evidence for electron transfer quenching in the dyads as such, whereas the addition of pyridine (that binds axially to zinc and thus affects the porphyrin redox potential) led to a moderately efficient photoinduced electron transfer process. In perspective, an appropriate functionalization of the bipy ligand and/or of the porphyrin chromophore might improve the thermodynamics and, thus the efficiency, of the photoinduced electron transfer process.     

Heterocyclic nitrogen base adducts of nickel(II)–di(2,4-dibromophenyl)carbazonate

The title complex was prepared and characterized by elemental and spectral analyses. The formation constants of various heterocyclic nitrogen base adducts with the Ni^II–di(2,4-dibromophenyl)carbazonate have been determined in a monophase by spectrophotometry at 25 ± 0.1 °C. The monodenatate and bidentate bases form penta- and hexa-coordinated adducts respectively with 1:1 stoichiometry for the metal chelate-base, whereas the unsaturated monodentate bases form hexa-coordinated adducts with 1:2 stoichiometry. The behaviour of saturated heterocyclic bases such as pyrrolidine, piperidine, hexamethyleneimine and morpholine towards the metal chelate has been studied, and the results are discussed in terms of steric hindrance, basicity and ring structure.     

The structure of adducts of benzaldoxime and m-chlorobenzaldoxime dehydrodimers with styrene

The reaction of m-chlorobenzaldoxime dehydrodimer with styrene gives two 1:1 adducts.The main product 7 is a bisnitrone. The minor product 8 has been shown by X-ray diffraction anal-ysis to possess the structure: ArCH(N=O)CH_2CH (Ph)O--N=CHAr. The two C=N bonds areall in Z configuration. The structure of the adducts from benzaldoxime dehydrodimer and styrene isalso assigned.     

氨基酸卟啉锌配合物对氨基酸酯的分子识别研究(英文)

用紫外可见吸收光谱滴定方法研究了一种新型的苏氨酸卟啉锌配合物(主体)对氨基酸酯(客体)的分子识别.这种锌卟啉可以与氨基酸酯形成 1:1和 1:2的两种加合物.氨基酸酯的氨基首先与氨基酸残基的羧基作用形成 1:1的加合物,然后与锌卟啉的中央锌原子配位形成 1:2的加合物,客体分子与主体分子上的氨基酸残基之间的排斥作用以及主客体之间的色散力作用是主体分子能识别客体分子的另外两种作用。     

Synthesis of nickel(II)-di(2,3-dichlorophenyl)carbazonate and its adduct formation with heterocyclic nitrogen bases

The nickel(II)-di(2,3-dichlorophenyl)carbazonate [Ni(D2,3DClPC)₂] complex has been prepared and characterized by elemental and spectral studies. The Ni^II chelate forms adducts with heterocyclic nitrogen bases, which were studied spectrophotometrically in monophase CHCl₃ media. Saturated monodentate bases such as pyrrolidine, piperidine, etc., form pentacoordinate adducts of 1:1 stoichiometry, whereas bidentate and unsaturated monodentate bases form hexacoordinated adducts with 1:1 and 1:2 metal–ligand stoichiometries respectively. The results are discussed interms of steric properties, basicity and ring structures of the heterocyclic bases.     

Mass spectrometric studies of the formation and reactivity of trans-[PtCl2(Am)(piperidinopiperidine)] x HCl complexes with ubiquitin

trans-[PtCl2(Am)(pip-pip)] x HCl complexes, where Am = ammine, methylamine and dimethylamine, react with ubiquitin to form 1:1 covalent adducts. The platinum complexes bind exclusively to Met1 of ubiquitin forming trans-[PtCl(S-Met1-Ub)(Am)(pip-pip)] adducts. These adducts are reactive towards nucleophiles and react with deoxyguanosine (dGMP) to form the ternary trans-[Pt(dGMP)(S-Met1-Ub) (Am)(pip-pip)] complex which is stable in water and even in the presence of excess glutathione (GSH). Reaction of trans-[PtCl(S-Met1-Ub)(Am)(pip-pip)] with GSH resulted in the rapid formation of the ternary complex trans-[Pt(GS)(S-Met1-Ub)(Am)(pip-pip)] which was not stable and slowly lost the platinum moiety; after 7 days the platinum moiety was completely removed and the native ubiquitin was regenerated.     

A novel and efficient synthesis of bicyclo[2.2.2]octenones and sigmatropic shifts in ground and excited states: stereoselective route to cis-decalins and diquinane frameworks

A new and efficient synthesis of a variety of highly embellished bicyclooctenones having an endo-vinyl moiety and their sigmatropic shifts in ground and excited states leading to a stereoselective route to substituted cis-decalins and diquinane frameworks have been described. Functionalized bicyclo[2.2.2]octenones having an endo-vinyl group and a beta,gamma-enone chromophore were prepared by in situ generation of 6-chloromethyl-6-hydroxycyclohexadienones and cycloaddition with butadiene (also generated in situ) followed by manipulation of the adducts. The presence of contiguous carbonyl, hydroxyl, and chloromethyl groups in adducts led to the introduction of various alkyl groups alpha to the ketone in a stereoselective fashion. The 3,3-sigmatropic shift in the bridged bicyclic compounds gave the corresponding cis-decalins, whereas the triplet sensitized irradiation led to the formation of diquinanes as a result of a 1,2-acyl shift.     

The hydrogen bond donor and acceptor ability of thioformic acid

The molecular orbital (MP2) and density functional theory calculations (B3LYP) using 6-311++G(2d,2p) basis set have been carried out on adducts of the cis and trans conformers of two tautomeric forms of thioformic acid (TFA) with water. Thirteen adducts of TFA with water have been optimized. Similar calculations have been carried out on adducts of formic acid with water and seven energy minima have been obtained for them. Our findings indicate that the specific interactions with water play an important role in the conformational stability as thiol form of TFA is the most stable form in gas phase, while it is the thione form which is the most stable in 1:1 adduct. The H-bond acceptor ability of S and O at the thiocarbonyl and carbonyl positions in TFA and FA, respectively, has been compared and observed to be only slightly lower in the former. However, the H-bond donor ability of S–H has been observed to be nearly half to that of O–H. The contributors to stabilization energies of adducts are explored by analyzing geometrical variations, atomic charges, and electron delocalizations.     

Strategies for synthesis of adducts of omicron-quinone metabolites of carcinogenic polycyclic aromatic hydrocarbons with 2'-deoxyribonucleosides

Polycyclic aromatic hydrocarbons (PAHs) are major environmental carcinogens produced in the combustion of fossil fuels, tobacco, and other organic matter. Current evidence indicates that PAHs are transformed enzymatically to active metabolites that react with DNA to form adducts that result in mutations. Three activation pathways have been proposed: the diol epoxide path, the radical-cation path, and the quinone path. The latter involves aldo-keto reductase mediated oxidation of PAH dihydrodiol metabolites to catechols that enter into redox cycles with quinones. This results in generation of reactive oxygen species (ROS) that attack DNA, and the PAH quinones also react with DNA to form adducts. Several strategies for synthesis of the stable adducts formed by the o-quinone metabolites of carcinogenic PAHs with 2'-deoxyribonucleosides were investigated and compared. The PAH quinones studied were benz[a]anthracene-3,4-dione and its 7-methyl- and 7,12-dimethyl- derivatives. The parent PAHs represent a range of carcinogenicity from inactive to highly potent. Two synthetic methods were devised that differ in the catalyst employed, Pd(OAc)(2) or CuI. The Pd-mediated method involved coupling a protected amino-catechol PAH derivative with a halo-2'-deoxyribonucleoside. The copper-mediated method entailed reaction of a halo-PAH catechol derivative with a 2'-deoxyribonucleoside. Adducts of benz[a]anthracene-3,4-dione (and its 7-methyl- and 7,12-dimethyl- derivatives) with 2'-deoxyadenosine and 2'-deoxyguanosine were prepared by these methods. Availability of adducts of these types through synthesis makes possible for the first time biological studies to determine the role of these adducts in tumorigenesis. The copper-mediated method offers advantages of economy, adaptability to large-scale preparation, utility for synthesis of (13)C- or (15)N-labeled analogues, and nonformation of bis-adducts as secondary products.     

The synthesis of amino acids by 1,3-dipolar cycloadditions of azomethine ylides

Thiazolium ylides react with a variety of dipolarophiles to afford adducts. After filtration chromatography, a tricyclic adduct is obtained. The tricyclic adducts react with potassium t-butoxide/t-butanol to provide dihydropyrroles. The adducts also react with tributyltin hydride to form compounds in which the thiazolidine ring has been cleaved. These adducts can be hydrolyzed under acidic conditions to form pyrrolidines. The desulfurization procedure is significant in that none of the relative asymmetry derived from the dipolar cycloaddition is lost. The synthesis of α-allokainic acid has been achieved from adduct 16s.     

导电聚合物膜修饰电极的研究Ⅲ: 杂多酸掺杂聚吡咯膜电极的电子自旋共振(ESR)特性研究

本文通过对不同条件下的Co(W~2O~7)~6^1^0^-和CuW~1~2O~4~0^6^-掺杂聚吡咯膜ESR谱线的分析并以相同条件下NO~3^-掺杂聚吡咯膜作为参照, 表明杂聚阴离子不仅起着中和电性的作用, 而且与聚吡咯分子链相作用形成某种加合物, 它影响聚吡咯的电结构, 这种加合物在过正或过负的电位下均不稳定。首次发现在CuW~1~2O~4~0^6^-掺杂的干态聚吡咯膜具有Dysonian线型, 表明膜中其它电结构的存在。     

Site-specific synthesis and reactivity of oligonucleotides containing stereochemically defined 1,N2-deoxyguanosine adducts of the lipid peroxidation product trans-4-hydroxynonenal

trans-4-Hydroxynonenal (HNE) is a major peroxidation product of omega-6 polyunsaturated fatty acids. The reaction of HNE with DNA gives four diastereomeric 1,N(2)-gamma-hydroxypropano adducts of deoxyguanosine; background levels of these adducts have been detected in animal tissue. Stereospecific syntheses of these four adducts at the nucleoside level have been accomplished. In addition, a versatile strategy for their site-specific incorporation into oligonucleotides has been developed. These adducts are destabilizing as measured by melting temperature when compared to an unadducted strand. The thermal destablization of the adducted 12-mers ranged from 5 to 16 degrees C and is dependent on the absolute stereochemistry of the adduct. The HNE adducts were also examined for their ability to form interstrand DNA-DNA cross-links when incorporated into a CpG sequence. We find that only one of the HNE stereoisomers formed interstrand DNA-DNA cross-links.     

Studies on cycloaddition of spiroepoxycyclohexa-2,4-dienones with indene and sigmatropic shifts in excited states: Synthesis of benzotricyclo[5.2.2.02,6]undec-10-en-9-ones,annulated polyquinanes and bicyclo[4.2.0]octanoids

A regio- and stereoselective cycloaddition of 6,6-spiroepoxycyclohexa-2,4-dienones with indene leading to benzo-annulated spiroepoxytricyclo[5.2.2.0^2,6]undec-10-en-9-ones has been described. Manipulation of the oxirane ring in adducts furnished benzotricyclo[5.2.2.0^2,6]undecanes endowed with a β,γ-enone chromophore. Photochemical reaction of β,γ-enones upon direct irradiation (1S) gave annulated bicyclo[4.2.0]octenones as a consequence of a stereoselective 1,3-acyl shift. Triplet excitation of chromophoric systems led to oxa-di-π-methane reaction and gave pentacyclic products which upon cleavage of cyclopropane ring furnished benzoannulated triquinanes. An interesting effect of substituent on the photoreaction has also been observed.     

Heteronuclear NMR investigation on the structure and dynamics of the chromophore binding pocket of the cyanobacterial phytochrome Cph1

Structural changes of the chromophore in phytochrome proteins associated with its photocycle are still not fully understood. We use heteronuclear NMR to investigate the conformation and dynamics of the chromophore in the binding pocket of the cyanobacterial phytochrome Cph1. On the basis of distance information obtained from three-dimensional nuclear Overhauser enhancement (3D-NOESY) spectra using the photochemically intact photosensory module of Cph1 we demonstrate that the chromophore is in the ZZZssa form in the P(r) (red absorbing form) state and the ZZEssa form in the P(fr) (far-red absorbing form) state of the protein. While ZZZssa for the P(r) state is in agreement with a recently determined X-ray structure, no comparable information for the P(fr) state of photochemically intact phytochrome has been available up to now. In addition, the chromophore in the binding pocket of Cph1 exhibits a notable mobility, which is distinctly different in the two photostates.     

Preparation and characterization of adducts of silicon tetrafluoride with thiazoles

Stable solid adducts of silicon tetrafluoride with the following thiazoles have been prepared: 2-aminothiazole, 2-amino-5-methylthiazole, 2-amino-6-methylbenzothiazole, 2-amino-7-nitrobenzothiazole and 2,4-dimethylthiazole. These adducts have been charactertsed by chemical and infrared spectral analysis. In all the cases except that of 2,4-dimethylthiazole (SiF₄·2L) the composition is 1:1. Both exocyclic and endocyclic nitrogen atoms are the coordinating centres in all the four cases while only endocyclic participates in coordination in the case of 2,4-dimethylthiazole. No indication has been found for the involvement of sulphur in coordination. Probable structures of these adducts have been proposed in which silicon is hexacoordinate.     

Phytochromes with noncovalently bound chromophores: the ability of apophytochromes to direct tetrapyrrole photoisomerization

Chromophore-apoprotein interactions were studied with recombinant apoproteins, oat phytochrome (phyA) and CphB of the cyanobacterium Calothrix PCC7601, which were both incubated with the bilin compounds biliverdin (BV) IXalpha, phycocyanobilin (PCB) and the 3'-methoxy derivative of PCB. Previously it was shown that CphB and its homolog in Calothrix, CphA, show strong sequence similarities with each other and with the phytochromes of higher and lower plants, despite the fact that CphB carries a leucine instead of a cysteine at the chromophore attachment position and thus holds the chromophore only noncovalently. CphA binds tetrapyrrole chromophores in a covalent, phytochrome-like manner. For both eyanobacterial phytochromes, red and far-red light-induced photochemistry has been reported. Thus, the role of the binding site of CphB in directing the photochemistry of noncovalently bound tetrapyrroles was analyzed in comparison with the apoprotein from phyA phytochrome. Both the aforementioned compounds, which were used as chromophores, are not able to form covalent bonds with a phytochrome-type apoprotein because of their chemical structure (vinyl group at position 3 or methoxy group at position 3'). The BV adducts of both apoproteins showed phytochrome-like photochemistry (formation of red and far-red-absorbing forms of phytochrome [P(r) and P(fr) forms]). However, incubation of the oat apophytochrome with BV primarily yields a 700 nm form from which the P(r)-P(fr) photochemistry can be initiated and to which the system relaxes in the dark after illumination. The results for CphB were compared with a CphB mutant where the chromophore-binding cysteine had been introduced, which, upon incubation with PCB, shows spectral properties nearly identical with its (covalently binding) CphA homolog. A comparison of the spectral properties (P(r) and P(fr) forms) of all the PCB- and BV-containing chromoproteins reveals that the binding site of the cyanobacterial apoprotein is better suited than the plant (oat) phytochrome to noncovalently incorporate the chromophore and to regulate its photochemistry. Our findings support the proposal that the recently identified phytochrome-like prokaryotic photoreceptors, which do not contain a covalently bound chromophore, may trigger a light-induced physiological response.     

Lithium-iodine solid electrolyte galvanic cells using iodine adducts of nylon-6 as active materials of positive electrodes

Iodine and nylon-6 form adducts containing 70–90 wt-% of iodine on heating at 115–145°C. The adducts have electrical conductivities ranging from 10^?7 to 10^?3 S cm^?1 at 25°C, and the electrical conductivity increases with increasing content of iodine of the adduct. The activation energies of the electrical conduction for the adducts prepared at 115°C and containing 69.2, 81.8, 87.1, and 90.0 wt-% of iodine are 94.6, 67.0, 52.9, and 46.1 kJ/mol, respectively. Polyamides other than nylon-6 also form similar semiconducting adducts with iodine. IR and NMR spectroscopic analyses of the iodine—nylon-6 adducts indicate profound changes in the structure of nylon-6 on adduct formation and suggest the formation of a ?CN⁺H species. The iodine-nylon-6 adducts prepared at 115°C and containing more than 82 wt-% of iodine serve as good active materials of positive electrodes in lithium-iodine solid electrolyte galvanic cells (outer diameter = 11.6 mm; outer thickness = 2.0 mm). The current efficiencies of the galvanic cells at 500 kΩ load are about 50% based on the iodine added. Discharge at 100 kΩ load gives lower current efficiencies. The galvanic cell has an internal resistance of about 5 kΩ at 25°C before discharge, and the internal resistance increases to about 100 kΩ at about 40% discharge. The dependence of the internal resistance during discharge have been determined.