On Trivial Extensions of 2-Fundamental Algebras #

There are considered trivial extensions of minimal 2-fundamental algebras. It is shown that if the Auslander–Reiten quiver Γ _A of a minimal 2-fundamental algebra A contains a starting component or an ending component which is not generalized standard, then the Auslander–Reiten quiver Γ _T(A) of the trivial extension T(A) of A contains also a component that is not a generalized standard.     

The mass spectra of some selenoureas and selenothiocarbamic esters

The mass spectra of five selenoureas and two selenothiocarbamic esters are reported and discussed. Fragmentation modes are compared with those reported for the ureas, thioureas, carbamates and thiocarbamates.     

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.     

The mass spectra of halogeno derivatives of quinoxaline

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

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.

     

Sensitive electrospray mass spectrometry analysis of one-bead-one-compound peptide libraries labeled by quaternary ammonium salts

A rapid and straightforward method for high-throughput analysis of single resin beads from one-bead-one-compound combinatorial libraries with high resolution electrospray ionization tandem mass spectrometry (HR ESI-MS/MS) is presented. The application of an efficient method of peptide derivatization by quaternary ammonium salts (QAS) formation increases ionization efficiency and reduces the detection limit, allowing analysis of trace amounts of compounds by ESI-MS. Peptides, synthesized on solid support, contain a new cleavable linker composed of a Peg spacer (9-aza-3,6,12,15-tetraoxa-10-on-heptadecanoic acid), lysine with ?-amino group marked by the N,N,N-triethylglycine salt, and methionine, which makes possible the selective cleavage by cyanogen bromide. Even a small portion of peptides derivatized by QAS cleaved from a single resin bead is sufficient for sequencing by HR ESI-MS/MS experiments. The developed strategy was applied to a small training library of α chymotrypsin substrates. The obtained results confirm the applicability of the proposed method in combinatorial chemistry.