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Die Struktur von Dactylin vÄ/ird zu (I) ermittelt.

The crystal structure of the title compound, [Cu(ClsH20N204) (H20)].2H20. C2HsOH, has been determined and refined by three-dimensional least-squares techniques. The crystals are orthorhombic, space group P21212~, Z=4, with a=15.545 (1), b=16-121 (2) and c=8-6838 (5).~. Diffractometer intensity data were collected for all unique reflections with 0 < 75 °, using Ni-filtered Cu Ko~ radiation. The final R--3.5 % for all 2546 data. The estimated standard deviations are between 0.003 and 0.007 ,~ for all C, N and O atoms. The coordination of the copper(II) ion is best described as square pyrimidal. Polymerlike chains are formed in the solid state by the bridging of copper(II) ions with the terminal carboxyl groups in a direction parallel to the twofold screw axis in the c direction. Hydrogen bonds involving the water molecules, ethanol molecule and the peptide join the chains largely in the a direction. IntroductionAs part of a general study of the influence of transition metal cations on the conformation of amino acids and peptides we have determined the crystal structure of the copper(II) chelate of L-leucyl-L-tyrosine (CULT). Previously it has been reported that an interaction occurs between the Cu z+ ion and the activated aromatic ring of the tyrosine residue in the copper(II) chelates of both glycyl-L-leucycl-L-tyrosine (Franks & Van der Helm, 1971) and L-tyrosine (Van der Helm & Tatsch, 1972). It was, therefore, of interest to ascertain the position of the tyrosine side chain of CULT with respect to the Cu z+ ion. It was determined that although the conformations of the side chains were approximately the same for all three structures, a close contact was not observed in CULT. This interaction takes on added significance when one considers these molecules as possible model compounds for the active site in copper containing oxidases. Because activated * Supported by N. I. H. Development Award K4-GM-42, 572.aromatic rings are often substrates for these enzymes one might suggest that bonding at the active site, with subsequent electron transfer, takes place through the n-electrons of the aromatic ring.The purpose of this communication is to present the description of the structure of CULT and to compare this structure to those in which an interaction has been observed. ExperimentalThe compound CULT was prepared by Ieacting Lleucyl-L-tyrosine, copper sulfate and barium hydroxide in molar proportions of 1:1:1. The precipitate of barium sulfate was removed by centrifugation. The resulting solution was approximately 0.05 M in concentration of complex. The solution was then diluted with an equal volume of ethanol and after a few hours deep-blue needles crystallized from solution. These crystals were redissolved in water and a few drops of ethanol were added each day for several days. After three days deep-blue plates crystallized from the solution. The plate face is the (100) plane while the crystals are elongated along the c axis. During collection of STRUCTURE OF THE COPPER(II) CHELATE OF L-LEUCYL-L-TYROSINEdata it was...

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Zatosetron maleate is a potent, selective 5-hydroxytryptamine receptor antagonist. In anticipation of commercialization, a manufacturing synthesis of zatosetron from tropinone and 5-chlorosalicylic acid was developed. Development efforts focused on addressing several key issues including the supply and quality of the critical raw material tropinone, improvements in the stereoselective formation of 3-endo-tropanamine, and the compatibility with existing manufacturing capabilities of process requirements for the Claisen rearrangement used to produce a crucial benzofuran intermediate. The results of these studies and an improved route to zatosetron maleate are described.