α-Cyclisation of tertiary amines. Part 4. Cyano-imidoyl substituted furans from captodative enamines and dibenzoylacetylene

α-Cyano-enamines and dibenzoylacetylene lead to dienes (via [2+2] cycloaddition followed by ringopening). Their α-Cyclisation to oxygen produces the title compounds.     

Quantification of the anticancer agent STI-571 in erythrocytes and plasma by measurement of sediment technology and liquid chromatography-tandem mass spectrometry

An isocratic high-performance liquid chromatographic method coupled to tandem mass spectrometry for the quantification of the revolutionary and promising anticancer agent STI-571 (tradenames Gleevec, Glivec, Imatinib) in blood plasma and red blood cells (RBCs) is described. The method involves measurement of sediment technology for RBCs and a subsequent single protein precipitation step by the addition of acetonitrile to both the RBC isolate and plasma. The sample mixture was centrifuged (10 min, 3600 g), and the supernatant filtered through a HPLC filter (0.45 microm). The analytes of interest, STI-571 and the internal standard [2H8]STI-571 were eluted on a Waters Symmetry C18 column (50x2.1 mm I.D., 3.5 microm particle size) using a methanol-0.05% ammonium acetate (72:28, v/v) mixture. STI-571 and [2H8]STI-571 were detected by electrospray tandem mass spectrometry in the positive mode, and monitored in the multiple reaction monitoring transitions 494>394 and 502<394, respectively. The lower limit of quantitation of STI-571 was 2.1 ng/ml in RBCs and 1.8 ng/ml in plasma. The recovery from both plasma and RBCs was between 65 and 70%. The method proved to be robust, allowing simultaneous quantification of STI-571 in RBCs and plasma with sufficient precision, accuracy and sensitivity and is useful in monitoring the fate of this signal transduction inhibitor in whole blood of cancer patients.     

Vinylcyclopropylacyl and polyeneacyl radicals. Intramolecular ketene alkyl radical additions in ring synthesis

Treatment of a variety of substituted vinylcyclopropyl selenyl esters, e.g. 11, with Bu(3)SnH-AIBN in refluxing benzene leads to the corresponding acyl radical intermediates, which undergo rearrangement and intramolecular cyclisations via their ketene alkyl radical equivalents producing cyclohexenones in 50-60% yield. By contrast, treatment of conjugated triene selenyl esters, e.g. 32, with Bu(3)SnH-AIBN produces substituted 2-cyclopentenones via intramolecular cyclisations of their ketene alkyl radical intermediates. Under the same radical-initiating conditions the selenyl esters derived from o-vinylbenzoic acid and o-vinylcinnamic acid undergo intramolecular cyclisations producing 1-indanone and 5,6-dihydrobenzocyclohepten-7-one respectively in 60-70% yields. A tandem radical cyclisation from the alpha,beta,gamma,delta-diene selenyl ester 31 provides an expeditious synthesis of the diquinane 35 in 69% yield.     

Tandem cyclisations involving alpha-ketenyl alkyl radicals. New syntheses of the natural triquinanes pentalenene and modhephene

New synthetic approaches to the angular and propellane sesquiterpene triquinanes (+/-)-pentalenene 2 and (+/-)-modhephene 3, respectively, are described. The syntheses are based on tandem cyclisations involving alpha-ketene alkyl radical intermediates produced from alpha,beta-unsaturated acyl radical species, as highlighted in Schemes 2 and 4.     

The small Kakeya sets in,a conic

A Kakeya set in the linear representation , a nonsingular conic, is the point set covered by a set of lines, one through each point of . In this article, we classify the small Kakeya sets in . The smallest Kakeya sets have size , and all Kakeya sets with weight less than are classified: there are approximately types.     

Graphit-hexachloroplatinat(IV) und Platin(IV)-chlorid-Graphit. Übergang eines Graphitsalzes in eine Metallchlorid-Graphitverbindung

Graphite hexachloro-platinate(IV) and platinum(IV) chloride graphite. Transition of a graphite salt into a metal chloride-graphite compound Whereas graphite does not react with PtCl₄ in Cl₂ atmosphere up to 350°C, with H₂PtCl₆ · xH₂O at 150°C graphite hexachloroplatinate (third intercalation stage) is obtained. The thermal decomposition of the graphite salt gives PtCl₄-graphite with the composition near [C₄₂]_Gr · PtCl_4,3.     

The largest Erdős-Ko-Rado sets of planes in finite projective and finite classical polar spaces

Erd?s-Ko-Rado sets of planes in a projective or polar space are non-extendable sets of planes such that every two have a non-empty intersection. In this article we classify all Erd?s-Ko-Rado sets of planes that generate at least a 6-dimensional space. For general dimension (projective space) or rank (polar space) we give a classification of the ten largest types of Erd?s-Ko-Rado sets of planes. For some small cases we find a better, sometimes complete, classification.     

The Kakeya problem: a gap in the spectrum and classification of the smallest examples

Kakeya sets in the affine plane $\mathrm AG (2,q)$ are point sets that are the union of lines, one through every point on the line at infinity. The finite field Kakeya problem asks for the size of the smallest Kakeya sets and the classification of these Kakeya sets. In this article we present a new example of a small Kakeya set and we give the classification of the smallest Kakeya sets up to weight $\frac{q(q+2)}{2}+\frac{q}{4}$ , both in case $q$ even.