Über Heterocyclen, 13. Mitt.: Zur Struktur der Spiro-(2-oxo- bzw. 2-thionohexahydropyrimidin-4,2′-chromane)

Zusammenfassung Die Struktur der Spiro-(2-oxo- bzw. 2-thionohexahydropyrimidin-4,2-chromane) wird durch Synthese gesichert.

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The structure of spiro-2-oxohexahydropyrimidine-4,2-chromanes and spiro-2-thionohexahydropyrimidine-4,2-chromanes is proved by synthesis.

     

Enantioselective High-Throughput Assay Showcased for the Identification of (R)- as well as (S)-Selective Unspecific Peroxygenases for C−H Oxidation

Identifying (bio)catalysts displaying high enantio-/stereoselectivity is a fundamental prerequisite for the advancement of asymmetric catalysis. Herein, a high-throughput, stereoselective screening assay is reported that gives information on enantioselectivity, stereopreference and activity as showcased for peroxygenase-catalyzed hydroxylation. The assay is based on spectrophotometric analysis of the simultaneous formation of NAD(P)H from the alcohol dehydrogenase catalyzed enantioselective oxidation of the sec-alcohol product formed in the peroxygenase reaction. The assay was applied to investigate a library comprising 44 unspecific peroxygenases (UPOs) containing 25 UPOs not reported yet. Thereby, previously non-described wild-type UPOs displaying (S)- as well as (R)-stereoselectivity for the hydroxylation of representative model substrates were identified, reaching up to 98 % ee for the (R)- and 94 % ee for the (S)-enantiomer. Homology models with concomitant docking studies indicated the structural reason for the observed complementary stereopreference.     

Time-optimal torus theorem and control of spin systems

Given a compact, connected Lie group G with Lie algebra . We discuss time-optimal control of bilinear systems of the form

Coisotropic displacement and small subsets of a symplectic manifold

We prove a coisotropic intersection result and deduce the following: (a) Lower bounds on the displacement energy of a subset of a symplectic manifold, in particular a sharp stable energy-Gromov-width inequality. (b) A stable non-squeezing result for neighborhoods of products of unit spheres. (c) Existence of a “badly squeezable” set in ${\mathbb R^{2n}}$ of Hausdorff dimension at most d, for every n ≥ 2 and d ≥ n. (d) Existence of a stably exotic symplectic form on ${\mathbb R^{2n}}$ , for every n ≥ 2. (e) Non-triviality of a new capacity, which is based on the minimal action of a regular coisotropic submanifold of dimension d.     

An optical receiver for eight-level data communication over step index plastic optical fiber

An optical receiver with automatic-gain-control transimpedance amplifier, linear post amplifier and linear line driver suitable for multilevel signals is presented. A large-diameter photodiode (400 μm) with an antireflection coating optimized for red light was integrated. These features enable the presented optical receiver to be a promising plastic optical fiber receiver. An error free (<10⁻⁸) 400 Mbit/s data rate over 50 m PMMA-step index plastic optical fiber (1 mm diameter) is achieved with eight-level pulse amplitude modulation (8-PAM).     

Vanadin-Bestimmungsmethoden

Ohne Zusammenfassung     

Buchbesprechungen

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Zur Bestimmung von freien o- und p-Stellungen in Phenolen: Methyl- und Phenylsulfonylphenole

Zusammenfassung Es wird gezeigt, daß die Methode der Bromtitration nachB. Smith bei Methylsulfonylphenolen in etwas modifizierter Form gut zur Bestimmung der Zahl freier o- und p-Stellen geeignet ist. Bei Phenylsulfonylphenolen (Hydroxydiphenylsulfonen) ist dieses Verfahren nur beschränkt verwendbar.