13C-NMR-spektren stereoisomerer 1,4-dialkylspiro[4.5]decan-derivate

The ¹³C NMR spectra of a series of 7-substituted 1,4-dialkylspiro[4.5]decanes and of suitable reference compounds are assigned and the derived substituent effects upon the chemical shifts are discussed. In particular, consideration of γ and δ-effects allows the differentiation between 1,4-cis- and 1,4-trans-compounds. Furthermore, the (relative) configuration of the chiral spiroatom C-5 is determined.     

Modeling spatial patterns in Dictyostelium

The life cycle of Dictyostelium discoideum provides a striking example of the transition from single cell behavior to multicellular cooperativity. In this paper the status of the attempts at making semiquantitative models of the aggregation phase of this cycle is reviewed. Specifically, it is discussed how the propagation of cAMP waves is a typical example of excitable signaling, which is then rendered unstable by coupling to cell chemotaxis. To investigate the streaming pattern that emerges from this clumping instability, we next turn to a new simulation strategy, which couples dynamical cell-like entities ("bions") to continuum chemical concentration fields. Finally, we discuss two directions for further research: One is the study of the robustness with respect to the variation of system parameters (such as the cell density) exhibited by the biological system, but not by any simple model. The other concerns going beyond the aggregation phase to tackle the three-dimensional problem of slug formation and motion.     

Über die Carotinoide Flavoxanthin und Chrysanthemaxanthin: 1H-NMR.-, 13C-NMR.- und Massen-Spektren und absolute Konfiguration. (Kritische Überprüfung veröffentlichter chemischer und physikalischer Daten)

On the Carotenoids Flavoxanthin and Chrysanthemaxanthin: ¹H-NMR., ¹³C-NMR. and Mass Spectra, Absolute Configuration, Survey of Published Data Very pure flavoxanthin ( 1 ) and chrysanthemaxanthin ( 2 ) have been reisolated from flower heads of Taraxacum officinale. Both compounds were characterized by chromatographic, chemical and chiroptical data and extensive NMR. measurements. Examination of many published data on 1 and 2 led to the conclusion that flavoxanthin has often been mistaken for chrysanthemaxanthin and vice versa. Chemical degradation of 1 and 2 to (?)-loliolide ( 5 ) coupled with NMR. evidence (ASIS, spin-decoupling, NOE) allowed the assignment of the absolute configurations of 1 and 2 . Thus (+)-flavoxanthin is (3S,5R,8R, 3′R,6′R)-5, 8-epoxy-5, 8-dihydro-β, ε-carotene-3, 3′-diol and (+)-chrysanthemaxanthin its C(8)-epimer.     

ABNORMAL EMBRYONIC DEVELOPMENT OF THE AMERICAN SEA URCHIN FOLLOWING ILLUMINATION OF GAMETES WITH VISIBLE LIGHT FROM A PHOTOTHERAPY UNIT

Abstract— The unfertilized oocytes and spermatozoa of the American sea urchin ( Arbacia punctulata ) were exposed to phototherapy lights in order to determine the effect of this treatment regimen on post-irradiation fertilization and embryonic development. Light treatment revealed dose-dependent abnormalities in fertilization and subsequent embryonic development.     

Syntheses and X-Ray Crystal Structures of 2-Aminoindenes and Aminocymantrenes

Substituted 2-aminoindenes have been synthesized in almost quantitative yields by reactions of amines such as methylpiperazine, trimethylethylenediamine, 1,4-diaza-cycloheptane and N,N′-dimethylethylenediamine with 2-indanone. The 2-aminoindenes can be deprotonated and reacted with BrMn(CO)₃(Py)₂ to produce the respective aminoindenyl-cymantrenes in yields between 55–70%. The X-ray crystal structures of 2-(methylpiperazine)indenyl-cymantrene 5 (P1 , a = 12.667(3) Å, b = 16.630(3) Å, c = 17.382(3) Å, α = 72.70(3)°, β = 74.59(3)°, γ = 88.66(3)°, V = 3364.1(12) Å ³, Z = 8, R1(2σ(I)) = 4.02%, wR2(2σ(I)) = 10.30%) and the HClO₄ adduct of 2-(trimethylethylenediamine)-indenyl-cymantrene 6 (Cc, a = 23.722(5) Å, b = 6.9080 Å, c = 13.264 Å, β = 111.77(3)°, V = 2018.6(7) Å 3, Z = 4, R1(2σ(I)) = 2.94%, wR2(2σ(I)) = 7.90%) were determined. In both complexes the indenyl-carbon bonded to nitrogen displays significantly longer bonds to manganese [223.5(3)–225.8(3) pm] than the other four carbon atoms [213.3(3)–219.1(3) pm]. The short indenyl-nitrogen bonds of 136.2(4) and 137.8(4) pm are indicative of a substantial multiple bond character. The complexation of Zn²⁺ by the nitrogen atoms of 6 results in significant shifts of the CO stretching frequencies.