The mass spectrometric fragmentation patterns of some biologically active 1,3,4-thiadiazoles

Mass spectra of some twelve derivatives of 1,3,4-thiadiazole are reported. The fragmentation scheme of the 1,3,4-thiadiazole ring is specific and indicative as to the structure. Derivatives of 5-phenyl-1,3,4-thiadiazoles show rearrangement to isothiocyanates.     

2,6-Dialkoxy-7-methylpurines

The preparation of unsymmetrical 2,6-dialkoxy-7-methylpurines (2), and 2-alkoxy-1,7-dialkyl-6-oxo-1,6-dihydropurines (5) is described. In contrast to1 and2, a facile thermal lactim-lactam rearrangement from hypoxanthines5 and7 into xanthines6 was observed.

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2,6-Dialkoxy-7-methylpurine

Zusammenfassung Die Darstellung von unsymmetrischen 2,6-Dialkoxy-7-methylpurinen (2) und 2-Alkoxy-1,7-dialkyl-6-oxo-1,6-dihydropurinen (5) wird beschrieben. Im Gegensatz zu den Verbindungen1 und2 erfolgt die thermische Lactim-Lactam-Umlagerung der Hypoxanthine5 und7 zu den Xanthinen6 glatt.

     

The problem of amino acid complementarity and antisense peptides

The review presents three hypotheses concerning the amino acid complementarity: 1) the Mekler-Blalock antisense hypothesis; 2) the Root-Bernstein approach based on stereochemical complementarity of amino acids and anti-amino acids coded by anticodons read in parallel with the coding DNA strand; 3) Siemion hypothesis resulting from the periodicity of the genetic code. The current state of knowledge as well as the results of the implementations of these hypotheses are compared. A special attention is given to Root-Bernstein and Siemion hypotheses, which differ in only few points of the complementarity prediction. We describe methods of investigation of peptide-antipeptide pairing, including circular dichroism, mass spectrometry, affinity chromatography and other techniques. The biological applications of complementarity principle are considered, such as search for bioeffector-bioreceptor interaction systems, the influence of peptide-antipeptide pairing on the activity of peptide hormones, and the application of antipeptides in immunochemistry. The possible role of amino acid-anti-amino acid interactions in the formation of the spatial structures of peptides, proteins and protein complexes is discussed. Such problems as the pairing preferences of protein-protein interfaces, the role of the pairing in the creation of disulfide bonds and the possible appearance of such interactions in beta-structure are also examined. The main intention of the paper is to bring the complementarity problem to the attention of the scientific community, as a possible tool in proteomics, molecular design and molecular recognition.     

Immobilization of a cationic ruthenium(II) complex containing the hemilabile phosphaallyl ligand in hexagonal mesoporous silica (HMS) and application of this material as hydrogenation catalyst

The cationic ruthenium(II) complex [(η⁵-MeC₅H₄)Ru(η³-PPh₂CHCH₂)(η¹-PPh₂CHCH₂)]⁺ (1) containing the hemilabile phosphaallyl ligand in two different coordination modes has been immobilized inside the pores of aluminated hexagonal mesoporous silica HMS(Si/Al = 40) by direct ion exchange method. This material was characterized by X-ray diffraction, thermogravimetric analysis, FTIR, solid state NMR (²⁹Si, ²⁷Al), UV-Vis, and X-ray photoelectron spectroscopies. The textural properties were determined from nitrogen adsorption at 77 K. (1)/HMS(Si/Al = 40) was shown to be active and selective in the catalytic hydrogenation of phenylacetylene.     

The mass spectra of halogeno derivatives of quinoxaline

The mass spectra of seventeen different quinoxaline halogeno derivatives are reported. The fragmentation mechanism is discussed.     

Synthesis and structural investigation of the cyclochiral boron resorcinarenes obtained from l-amino acids and phenylboronic acid

A diastereoselective synthesis and structural investigation of novel boron derivatives of resorcinarenes from l-amino acids and phenylboronic acid is described.     

Synthesis and Fhotochemical Eroferties of Pyrimidine-6-Azafyrimidine Analcgs of Dinucleotides with Profanone Bridge

Dinucleotide analogs in which uracil and 6-azauracil derivatives are connected by propanone bridge were synthesized. Non-bonded base-base interaction and photochemical behaviour of these compounds were investigated.