New derivatives of 2-mercaptobenzotellurazole

New derivatives of 2-mercaptobenzotellurazole at the three reaction centers, the thiol group, nitrogen atom and tellurium atom, have been synthesized.     

The study and characterization of nucleosides by mass spectrometry—I: The mass spectra of pyrimidine 2,2′-anhydronucleosides and their derivatives

The mass spectra of 2,2′-anhydrouridine, 2,2′-anhydrothymidine and 2,2′-anhydro-4-thiouridine are reported. The acetyl, trifluoroacetyl, trityl, pivaloyl and trimethylsilyl ether derivatives were also studied. Deuterium labeling in acetyl and trimethylsilyl groups aided characterization of many ions in the spectra, as well as helping to clarify hydrogen migration processes. The anhydronucleosides and their derivatives are readily distinguished from natural nucleosides by the presence of an ion containing the base moiety plus the anhydro-ring plus one hydrogen atom from the rest of the molecule. As for natural nucleosides the [base + H]⁺ and [base + 2H]⁺ ions are usually prominent, but in contrast to natural nucleosides, ions characteristic of the sugar moiety do not retain the 2′-oxygen atom (i.e. the oxygen atom of the anhydro-ring). The mass spectra of deuterium labeled derivatives suggest a test for the presence of a 3′-O-acetyl function (the O-acetyl group is lost from the molecular ion much more readily from the 3′- than from the 5′-carbon atom). The trimethylsilyl derivatives showed evidence in their mass spectra for migration of trimethylsilyl groups in addition to hydrogen atoms.     

Conformational analysis of 3-borabicyclo[3.3.1]nonane derivatives

Conformations of 3-borabicyclo[3.3.1]nonane derivatives have been studied by means of ¹H and ¹³C NMR spectroscopy. With the aid of the coupling constants ³J(HH) and ¹³C chemical shifts it has been shown that all the derivatives of 3-borabicyclo[3.3.1]nonane with the trigonal boron atom studied are in a flattened double-chair conformation. In 3-borabicyclo[3.3.1]nonane derivatives with the tetra-coordinated boron atom and substituents at the 7α-position, the chair-boat conformation predominates, the boat conformation being characteristic of the cyclohexane ring; exceptions are the compounds with the internal donor—acceptor bond between the boron atom an 7α-substituent.     

单萜吲哚生物碱Uleine及其衍生物的合成进展

生物碱uleine及其衍生物从结构上看属于单萜吲哚生物碱,它们共同的结构特征是吲哚核与碱性氮原子之间只有一个碳相隔,而不像其它单萜吲哚生物碱有两个碳原子.由于其结构特异,天然含量少,因而其合成工作一直吸引着化学工作者.总结uleine生物碱及其衍生物的合成方法,根据构建环的种类不同,把合成方法分为五类.大部分方法都是以吲哚和吡啶衍生物为起始原料进行四环的合成,有几条合成路线简短易行.     

Unusual Reactivity of (Vinylimino)phosphoranes and Their Utility in the Preparation of Pyridine and Dihydropyridine Derivatives

New reactions of (vinylimino)phosphoranes with aldehydes involving an initial nucleophilic attack of the beta-carbon atom of the vinyl side chain on the carbonyl carbon atom are reported. Iminophosphorane 4 derived from ethyl beta-azidoacrylate reacts with substituted cinnamyl aldehydes to give a mixture of 2-arylpyridine and 4-styryldihydropyridine derivatives, whereas the reaction with substituted benzaldehydes provides 4-aryldihydropyridine derivatives. However, the iminophosphorane 16 derived from the diethyl azidofumarate reacts with cinnamyl aldehydes through the expected aza-Wittig fashion to give 4-arylpyridine derivatives after dehydrogenation of the resulting dihydropyridine.     

Fragmentations of peptide derivatives depending on the positions of proline in negative-ion fast atom bombardment mass spectrometry

Fragmentations of N-benzyloxycarbonyl-protected tripeptide ethyl esters, in which changes in the numbers and positions of prolyl residues were observed, were examined by negative-ion fast atom bombardment mass spectrometry. A significant difference was found among the intensities of the fragment ions formed by cleavage of the benzyloxycarbonyl group, depending on the numbers and positions of prolyl residues in the derivatives. These results suggest that the fragmentations of the peptide derivatives in negative-ion fast atom bombardment mass spectrometry depend on the conformational differences in the peptide derivatives due to the existence of proline, and permit the prediction of the positions of proline in the peptides.     

Alkylation of 3-aminoisocarbostyryl derivatives

The alkylation of derivatives of 3-aminoisoquinolin-1(2H)-one in the presence of NaH may proceed in three directions: 1) at the carbonyl group oxygen atom, 2) at the nitrogen atom N-2, and 3) at the 3-amino group. The reaction of equivalent amounts of the reagents gives predominantly products of substitution at the 3-amino group. Repeated alkylation proceeds at the lactam fragment to give a mixture of O-alkyl and N-alkyl derivatives. Acylation of 3-dialkylamino- and 3-alkylanilinoisoquinolin- 1(2H)-ones in the presence of NaH gave derivatives of 3-amino-1-isoquinolinyl 4-ethoxybenzoate.     

Spectra and structure of mercury derivatives of primary nitramines

The mercury derivatives of primary nitramines were proved by molecular spectroscopy and quantum-chemical calculations to be covalent compounds. The mercury atom was found to be coordinated to the amine nitrogen atom.     

Derivatization procedures for the detection of beta(2)-agonists by gas chromatographic/mass spectrometric analysis

An evaluation of derivatization procedures for the detection of beta(2)-agonists is presented. The study was performed with the beta(2)-agonists bambuterol, clenbuterol, fenoterol, formoterol, salbutamol, salmeterol and terbutaline. Different derivatizating agents were employed, aiming to obtain derivatives with high selectivity to be used in the gas chromatographic/mass spectrometric analysis of beta(2)-agonists in biological samples. Trimethylsilylation was compared with different agents and the role of some catalysts was evaluated. Acylation, combined trimethylsilylation and acylation, and the formation of cyclic methylboronates were also studied. Sterical hindrance caused by different substituents at the nitrogen atom of the beta-ethanolamine lateral chain of beta(2)-agonist molecules is mainly responsible for differences in the abundances of the derivatives obtained. The use of catalysts produces an increase in the derivatization yield, especially for compounds with low steric hindrance (substituents with primary and secondary carbon atoms). The formation of trimethylsilyl (TMS) ethers is not influenced by structural molecular differences when only hydroxy groups are involved in derivatization. Combined trimethylsilylation and acylation showed that compounds with a secondary carbon atom linked to the nitrogen atom form mainly N-TFA-O-TMS derivatives, with a small amount of N-TMS-O-TMS derivatives. Compounds with tert-butyl substituents at the amino group (bambuterol, salbutamol and terbutaline) formed O-TMS derivatives as the main products, although a limited amount of trifluoroacylation at the nitrogen atom also occurred. Cyclic methylboronates were formed with bambuterol, clenbuterol, formoterol, salbutamol and salmeterol. Owing to hydroxy substituents in unsuitable positions for ring formation, this procedure was not effective for fenoterol and terbutaline. Mass spectra of different derivatives and tentative fragmentation profiles are also shown. For screening purpose (e.g. sports drug testing), derivatization with MSTFA or BSTFA alone is recommended as a comprehensive derivatization technique for beta(2)-agonists owing to minimal by-product formation; formation of cyclic methylboronates can be useful for confirmation purposes. Detection limits were obtained for the TMS and cyclic methylboronate derivatives using the derivatizing reagents MSTFA and trimethylboroxine, respectively. For most of the compounds, lower detection limits were found for the TMS derivatives.     

Regioselective acetylation of some N-methylpyrrole derivatives with isopropenyl acetate and different acetic anhydrides

We studied the reactions of some N-methylpyrrole derivatives with isopropenyl acetate and different acetic anhydrides. We have found that the reaction with isopropenyl acetate afforded 5-acetylpyrrole derivatives while with acetic anhydrides acetylation occurred on the α-carbon atom of the side-chain of pyrrole-2-acetic acid derivatives.     

Photoelectron spectroscopy study of the triphenyl derivatives of the group IV elements

The photoelectron He(I) spectra of several phenyl derivatives of the Group IV elements are reported, and the first few bands are assigned to the corresponding MO's. A sizable interaction among the π orbitals of the rings has been found for the carbon derivatives HCPh₃, HC(mesityl)₃ and H₂CPh₂, but not for the Si, Ge and Sn triphenyl derivatives. The exceptional behaviour of the carbon compounds has been attributed to the short central atom—ring distance, by analogy with findings for the Group V triphenyl derivatives.The charge transfer from the rings towards the Si atom is substantially reduced compared with that in H₃SiPh.     

Reaction of dichlorophosphorylimidophosphorus trichloride with nucleophilic reagents

Conclusions When dichlorophosphorylimidophosphorus trichloride is reacted with nucleophilic reagents (phenols, dialkylamines, and their trimethylsilyl derivatives), the first to be replaced is the chloride atom on the imido P atom. As the result of further reaction with phenol the substitution at the imido P atom continues, while when reaction is with diethylamine or diethylaminotrimethylsilane the chlorine atom on the phosphoryl P atom is replaced.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2379–2386, October, 1980.     

Phenoxy Derivatives of Dicyclopentadienyl Tungsten(VI) Oxydichloride and Bisindenyl Tungsten (VI) Oxydichloride

Phenoxy complexes containing π-bonded cyclopentadienyl and indenyl groups attached to metals ytterbium¹⁾, titanium¹⁾, and cerium¹⁾. are reported in the literature. These phenoxide derivatives were prepared by the actious of various phenols on the cyclopentadienyl or indenyl metal halide complexes in benzene or tetrahydrofuran. There is no mention the literature about the prepartion and characterization of phenolic derivatives of π-cyclopentadienyl and π-indenyl oxotungsten (VI). The effect of electron releasing or electron attracting substiuents in the phenols on the nature of the complexes and the metal-phenoxide bond has not been reported. The possibility of formation of hydrogen bond between hydrogen atom of the free hydroxyl group of a polyhydric phenoxide group and the oxygen atom attached to the metal atom has not also been explored. This communication deals with such an attempt and reports the synthesis and characterization of 26 phenoxy derivatives of dicyclopentadienyl and bisindenyltungsten (VI) oxydichlorides and conclusions derived from their infrared spectral study.     

Condensed thienopyrimidines. II. Synthesis and gastric antisecretory activity of thiazole and polymethylene condensed thienopyrimidine derivatives

Thiazolo[3,2-a]thieno[3,2-d]-, [3,4-d]- and [2,3-d]pyrimidin-5-one derivatives (6, 11 and 16), and polymethylene condensed thieno[3,2-d]-, [3,4-d]- and [2,3-d]pyrimidin-5-one derivatives (19-21), in which the oxygen atom of the oxazolidine moiety in 3 was replaced by a sulfur atom or methylene groups, were synthesized and evaluated for gastric antisecretory activity in pylorus-ligated rats. The structure-activity relationships of these compounds are discussed.     

Characteristic fragmentations of peptide derivatives containing proline in negative-ion fast atom bombardment mass spectrometry

Fragmentations of N-benzyloxycarbonyl-protected tripeptide ethyl esters containing proline were compared with those of the corresponding peptide derivatives not containing proline in negative-ion fast atom bombardment mass spectrometry. The fragment ion [M – 109]^? due to loss of the benzyloxy group followed by dehydrogenation from the peptide molecule was the base peak in the negative-ion mass spectra for the peptides not containing proline, whilst it was a very weak fragment ion or not observed at all in those for the peptides containing proline. These results suggest that the fragmentations of the peptide derivatives in negative-ion fast atom bombardment mass spectrometry depend on the conformational difference of the peptide derivatives owing to the existence of proline in the derivative.     

Polymethine dyes — Benzofuro[2,3-b]pyridine and selenonaphtheno[2,3-b]pyridine derivatives

Polymethine dyes — benzofuro[2,3-b]pyridine and selenonaphtheno[2,3-b]pyridine derivatives — were synthesized, and their spectral properties are discussed. Replacement of a vinylene group by an oxygen or selenium atom in one benzene ring of the 2-benzo[h]quinoline residue in the cyanines causes a large bathochromic shift of the absorption maxima of the dyes as compared with replacement by a sulfur atom. The dyes derived from benzofuro[2,3-b]pyridine derivatives are more deeply colored than the derivatives of both thionaphtheno[2,3-b]-pyridine and selenonaphtheno[2,3-b]pyridine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp.1611–1614, December, 1972.     

Structure électronique des isologues oxygénés du trithia-1,6,6aSiv pentalène: I. Nature De L'interaction SβO

Valence electron CNDO/2-SCF-MO calculations have been performed on some oxygenated derivatives of 1,6,6aS^IV-trithiapentalene. The calculations demonstrate the relative importance of the d orbitals for the central sulphur atom and a dΣ-pΣ interaction between this atom and the neighbouring oxygen atom.     

Fast atom bombardment mass spectrometric study of benzyloxycarbonyl-protected tetrapeptides containing proline

Fragmentations of N-benzyloxycarbonyl-protected tetrapeptide ethyl esters containing L -alanine and L -proline, in which changes in the numbers and positions of prolyl residues were observed, were studied by negative-ion fast atom bombardment mass spectrometry. A significant difference was found among the abundances of the molecule ions and the fragment ions formed by the cleavage of the benzyloxycarbonyl group, depending on the numbers and positions of prolyl residues in the derivatives. The results indicate that the conformational differences in the tetrapeptide derivatives due to the existence of proline affect fragmentations of molecules in the solution phase in negative-ion fast atom bombardment mass spectrometry.     

Cation complexation behavior of pyrene- and anthracene-appended new crown ether derivatives

Pyrene- and anthracene-appended new crown ether derivatives have been synthesized by Schiff's base reaction, and cation complexation behavior was investigated by fluorescence spectroscopy measurements. Based on photo-induced electron transfer and intramolecular charge transfer mechanism, the host molecules emit stronger fluorescence in the presence of various cations Na(+), K(+), Rb(+), Cs(+) and NH(4)(+) since the complexation between guest cations and crown ether compounds inhibit partial electron transfer from the nitrogen atom to the chromophores and subsequently fluorescence is enhanced. The binding constants were estimated from the plots of the fraction of binding sites filled for crown ether compound as a function of free-ion concentration. Results show that 15-crown-5 derivatives exhibit higher binding ability with sodium cations while 18-crown-6 derivatives had higher affinity for potassium cations, which is consistent with the hole-size relationship of the crown ethers. Ammonium ion complexation caused largest fluorescence enhancement. It is understood that ammonium ion cannot only complex with crown ether, but also interact directly with the lone pair electrons of nitrogen atom in C=N bond so that electron transfer from the nitrogen atom to chromophores is further inhibited.