Tricarbonyl (triquinacene)-molybdenum and-tungsten

Triquinacene reacts with hexacarbonylmolybdenum to give tricarbonyl(triquinacene)molybdenum, and with tris(acetonitrile)tricarbonyltungsten to give tricarbonyl(triquinacene)tungsten, whereas efforts to synthesize the corresponding chromium complex, tricarbonyl(triquinacene)chromium, were unsuccessful.The molybdenum complex was characterized by ¹H and ¹³C NMR spectroscopy, mass spectra, and a single crystal X-ray structure determination. The tungsten complex is thermally less stable and more susceptible to oxidation than its molybdenum analogue and was characterized by the mass spectrum and the ¹H NMR spectrum. The crystal structure of the tricarbonyl(triquinacene)molybdenum is compared to that for the free ligand. Besides the expected lengthening of the CC bonds, the complex shows a deepening of the triquinacene “basket”, presumably to give better overlap of the CC bonds with molybdenum orbitals.     

Crystal and moleclar structures of 5-allyl-25-methoxy-26,27,28-tribenzoylcalix[4]arene

The crystal and molecular structures of 5-allyl-25-methoxy-26,27,28-tribenzoylcalix[4]arene, an unsymmetrically substituted macrocycle, are reported. The space group is orthorhombic,P2₁2₁2₁, witha=13.4181(6),b=16.6652(10) andc=18.9936(14) Å andZ=4. Refinement by least-squares calculations converged with aR=0.060 for 4018 observed reflections. The molecule assumes a 1,3 alternate conformation with 2 benzoate rings and the disordered allyl side chain on one side and the third benzoate ring and the methoxy group on the opposite side of the mean plane of the methylene bridging groups. The four phenyl rings that comprise the macrocycle are approximately parallel in pairs; the members of a pair are 5.6 Å apart. The carbonyl oxygen atoms of the 3 benzoate groups are oriented away from the center of the cavity while the ester oxygen atoms and the methoxy oxygen atom are oriented toward the cavity center. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82033 (26 pages).     

Determination of citrulline in watermelon rind

Watermelon (Citrullus vulgaris Schrad.) is a natural and rich source of the non-essential amino acid citrulline. Citrulline is used in the nitric oxide system in humans and has potential antioxidant and vasodilatation roles. A method using gas chromatography-mass spectrometry (GC-MS) was developed to separate citrulline from glutamic acid, which co-elute when analyzed by high performance liquid chromatography. Watermelons were analyzed by GC-MS to determine the citrulline content among varieties, types, flesh colors, and tissues. Citrulline content ranged from 3.9 to 28.5 mg/g dry weight (dwt) and was similar between seeded and seedless types (16.6 and 20.3 mg/g dwt, respectively). Red flesh watermelons had slightly less citrulline than the yellow or orange flesh watermelons (7.4, 28.5 and 14.2 mg/g dwt, respectively). Rind contained more citrulline than flesh on a dry weight basis (24.7 and 16.7 mg/g dwt, respectively) but a little less on a fresh weight (fwt) basis (1.3 and 1.9 mg/g fwt, respectively). These results indicate that watermelon rind, an underutilized agricultural waste, offers a source of natural citrulline.     

The crystal and molecular structures of rac-threo-ifenprodil and two other 4-benzylpiperidinyl derivatives

The crystal structures of threo-ifenprodil [threo-2-(4-benzyl-piperidin-1-yl)-1-(4-hydroxyphenyl)-propan-1-ol] (1), potent NMDA receptor antagonist, and two related, biologically active compounds: threo-2-(4-benzyl-piperidin-1-yl)-1-(4-fluorophenyl)-propan-1-ol (2) and 4-benzyl-1-phenethyl-piperidinium chloride (3) have been determined by X-ray structure analysis of single crystals. Compound 1 crystallizes in an orthorhombic system, with a space group Pna2₁ (a = 34.843(3) Å, b = 6.0261(13) Å, c = 8.9343(9) Å), compound 2 – in a monoclinic space group P2₁/c (a = 14.194(1) Å, b = 6.2831(6) Å, c = 20.948(1) Å, = 101.762(6)), and compound 3 – in an orthorhombic space group Pbca (a = 10.4627(8) Å, b = 11.2166(6) Å, c = 31.669(2) Å). The piperidine rings are close to ideal chair conformations, the substituents are in equatorial positions. Overall shapes of the molecules, defined by the dihedral angles between the terminal aromatic rings, are very similar in all three cases. In 1 and 3 the crystal packing is mainly determined by the hydrogen bonds, while in case of 2 – by weak van der Waals interactions. The molecules of 1 and 3 are disordered, and the disorder is caused by a rotation around the N–C bond.     

Über das Thalliumheptagermanat Tl2Ge7O15

Zusammenfassung Im System Tl₂O–GeO₂ wird auf der GeO₂-reichen Seite neben den schon beschriebenen Verbindungen Tl₂Ge₄O₉, Tl₂Ge₅O₁₁ und Tl₂Ge₆O₁₃ ein weiteres Germanat, und zwar der Zusammensetzung Tl₂Ge₇O₁₅, aufgefunden. AusDK- undWeissenberg-Aufnahmen ergibt sich eine hexagonale Elementarzelle; die Gitterparameter betragen:a=12,67₃,c=7,46₀Å undc/a=0,589.