Crystal and molecular structure of 6-0-acetylgrayanotoxin III

The crystal and molecular structure of a grayanotoxin III derivative, 6-0-acetylgrayanotoxin III is presented. The crystal is orthorhombic, space group P2₁2₁2₁, witha=15.582(3),b=21.304(3),c=6.339(3)Å,V=2104(1) ų Z=4. The structure was solved by direct methods and refined by full matrix least-squares methods to a finalR=0.047 for 1763 independent reflections withF ₀>3 (F ₀) The molecule is based on a tetracyclic structure consisting of two five-membered, one six-membered, and one seven-membered ring with various conformations.     

13CNMR-Untersuchung der Taktizit?t von Poly-(RS)tert-butyloxiran, das durch Polymerisation mit tert-C4H9OK erhalten wurde

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1H-NMR study of polyisoprenes

¹H-NMR spectra of polyisoprene were assigned using polymers of isoprene-1,1,4,4-d₄, isoprene-1,1,5,5,5-d₅, and isoprene-4,4-d₂ polymerized with various catalysts. The methylene-proton signal at 2.1 ppm in cis-1,4 - and trans-1,4-polyisoprenes was divided into H₄- and H₁-proton signals; H₄ resonated at 2.21 ppm in both cis-1,4 and trans-1,4 units whereas H₁ resonated at 2.05, 2.21, and 2.15 ppm. Splitting due to the dyad sequences of 1,4 and 3,4 units was apparent. The methine-proton (H₃) in a 3,4 unit showed a broad peak centered around 1.5 ppm in C₆D₆. The overlapping of this signal with the methyl-proton signals at 1.73 and 1.63 ppm resulted in some uncertainty in the determination of the microstructure of polyisoprene which contained a considerable amount of 3,4 unit.     

Wechselwirkung zwischen entgegengesetzt geladenen Polypeptiden

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