Some new reference materials for organic elemental analysis: Their development and certification within the B. C. R. -Programme

Summary The procedure of manufacturing and certification of new reference materials intended to be used in organic elemental analysis is presented. The experience gained in the development of several materials has been used to design this procedure. A discussion of the requirements to be posed to a reference material in this field underlies the procedure. The results for five materials and the various methods used to obtain these results are given.

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Über einige Referenzmaterialien für die organische Elementaranalyse: deren Entwicklung und Certifizierung im Programm des B. C. R.

Zusammenfassung Die Arbeitsweise zur Entwicklung und Certifizierung neuer Referenzmaterialien für die organische Elementaranalyse wird angegeben. Zur Festlegung dieser Arbeitsweise wurde die Erfahrung bei der Entwicklung von mehreren Materialien angewendet. Das Verfahren gründet sich auf eine Diskussion der Anforderungen, die man an ein Referenzmaterial stellen muß. Die Ergebnisse von fünf Materialien sowie die verschiedenen Analysenmethoden, die zu diesen Ergebnissen führten, wurden angegeben.

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B. C. R.: Community Bureau of Reference; Commission of the European Community.     

Rapid parallel synthesis of dipeptide diphenyl phosphonate esters as inhibitors of dipeptidyl peptidases

In this paper, we present a parallel synthesis of several series of dipeptide diphenyl phosphonates that are known to be irreversible inhibitors of serine proteases. Polymer-assisted solution-phase synthesis (PASP) is used for the rapid and clean coupling between various alpha-aminoalkyl diphenyl phosphonate ester building blocks and commercially available or easily accessible amino acids. These compounds were used for the rapid profiling of dipeptidyl peptidase II (DPP II) and the closely related dipeptidyl peptidase IV (DPP IV). A highly selective DPP II inhibitor was identified, N-cyclopentylglycyl-NHCH(C(6)H(5))PO(OPh)(2) (9.35), that will be useful to discriminate between DPP II and DPP IV in biological systems in order to further elucidate the biological function of DPP II.     

Synthesis of 4-oxopyrimidinium and 4-oxo-1,4-dihydropyrimidines

The synthesis of N¹-substituted 4-pyrimidones is described. These compounds were prepared from their corresponding 4-oxopyrimidinium perchlorates or from a reaction of a primary amine with a N-acyl-β-ketoamide.     

On the length of longest chordless cycles

Upper bounds for the length of a longest (circuit) cycle without chords in a (directed) graph are given in terms of the rank of the adjacency matrix and in terms of its eigenvalues.Received: October 2003, Revised: January 2005, AMS classification: 05C     

The synthesis of some 2,4-disubstituted derivatives of quinolone-3-carboxylic acids and carbonitriles

In order to prepare the 2-chloro derivative of oxolinic acid, ethyl 1-ethyl-1,4-dihydro-2-hydroxy-6,7-methylenedioxy-4-oxo-3-quinolinecarboxylate was treated with phosphorus oxychloride. The compound obtained was the 4-chloro-2-oxo-quinoline. The structure was confirmed by ¹³C nmr and mass spectral techniques. The 2-halocarbonitrile was obtained by a Sandmeyer reaction but could not be hydrolysed into the acid.     

Quantum theory as the most robust description of reproducible experiments

It is shown that the basic equations of quantum theory can be obtained from a straightforward application of logical inference to experiments for which there is uncertainty about individual events and for which the frequencies of the observed events are robust with respect to small changes in the conditions under which the experiments are carried out.     

The graph with spectrum 141 240 (?4)10?(?6)9

We show that there is a unique graph with spectrum as in the title. It is a subgraph of the McLaughlin graph. The proof uses a strong form of the eigenvalue interlacing theorem to reduce the problem to one about root lattices.