Structural Aspects of the Enantioselectivity of Tartrates with α-Amino-alcohol Salts. Part II. Crystal structures of (1R, 2S)-norephedrine hydrochloride and (1R, 2R)- norpseudoephedrine hydrochloride

Enantioselective host-guest complexes between α-amino-alcohol salts and chiral tartrates can not be crystallised up to now. To study structural aspects of their enantioselectivity, crystal structures of the components were determined. Norephedrine was used as a reference guest α-amino-alcohol. (1R, 2S)-Norephedrine hydrochloride (monoclinic, space group P2₁ Z = 4, a = 8.455, b = 10.331, c = 12.570 Å, β = 107.45°) and (1R, 2R)-norpseudoephedrine hydrochloride (monoclinic, space group P2₁ Z = 2, a = 5.493, b = 8.052, c = 11.986 Å, β = 104.62°) both adopt M-synclinal conformations with respect to the ammonium and hydroxy groups. Rather short intramolecular N…?O distances indicate interaction between ammonium and hydroxy groups.     

Über Pterinchemie. 49. Mitteilung. Eine neue Synthese von 5-Formyl-6, 7-dimethyl-5,6,7,8-tetrahydropterin und 5,6,7-Trimethyl-5,6,7,8-tetrahydropterin

Starting with 5-formyl-6,7-dimethyl-5,6,7,8-tetrahydropterine (II), a new synthesis of 5,6,7-trimethyl-5,6,7,8-tetrahydropterine (III) is described. Thereby the chemical behaviour of the 5-formyl group in II is investigated, in order to enable the unequivocal differentiation between formylation at position 5 and at position 10 in folic and tetrahydrofolic acid derivatives. ¹³C-NMR. spectra of II and III are discussed.     

Chemical Synthesis,Proton NMR. Parameters,Hydrogen- and Calcium-Ion. Complexation of L-γ-Carboxyglutamyl-L-γ-carboxyglutamic Acid and D-γ-Carboxyglutamyl-L-leucine

The purpose of this communication is to describe the preparation and some properties of the first two synthetic peptides containing D - and L -γ-carboxyglutamic acid. Use was made of N-protected γ,γ′-di-t-butyl-γ-carboxyglutamic acids (D , L , and DL ) described earlier [1 a]. Preliminary ¹H-NMR. data (360 MHz) indicate a restricted rotation of the Gla side chain in the free amino acid as well as in the C-terminal Gla of Gla-Gla in H₂O solution at acid pH. The proton dissociation from Gla and Gla-Gla was studied by potentiometric titration and NMR. methods. The pH titration in the presence of Ca²⁺ ions shows that Gla-Gla has a much higher association constant for this cation than Gla. It is almost as great as that of prothrombin (pCa²⁺ = 3.2 vs. 3.5).     

Über Pterinchemie. Mitteilung. Die Kristallstruktur von 5,6,7-Trimethyl-5,6,7,8-tetrahydropterindihydrochlorid-monohydrat

The crystal structure of 5,6,7-trimethyl-5,6,7,8-tetrahydropterine-dihydrochloride-monohydrate The crystal structure of the title compound has been determined by X-ray analysis (direct methods) and refined with 947 structure amplitudes to R = 0.026. The crystal system is orthorhombic, space group Pna2₁, with unit cell dimensions a = 14.081, b = 14.623, c = 6.773 Å. The molecule is protonated at the N(1)- and N(5)-position. The tetrahydropyrazine ring exists in a conformation in which C(6) deviates markedly from the mean plane of the other five atoms. The CH₃-groups at N(5) and C(6) possess a trans configuration with a pseudoaxial and an axial conformation respectively. The CH₃-groups at C(6) and C(7) in return possess the cis configuration, whereby the CH₃-group at C(7) occupies an equatorial conformation.     

Cyclobut-2-enones from Alkynes via Dichlorocyclobut-2-enones

The [2 + 2]-cycloaddition of dichloroketene (prepared in situ from CCl₃COCl and Zn(Cu)) with three alkynes 1a–c to form 2,3-dimethyl-( 2a ), 2,3-diethyl-( 2b ) and 3-butyl-4,4-dichlorocyclobut-2-enone ( 2c ) proceeds rapidly in the absence of POCl₃. The primary products 2a–c rearrange in situ to the 2,4-dichlorocyclobut-2-enones 3a–c under the influence of ZnCL₂ produced during the reaction. ZnCl₂ converts both 2a and 3a into a 4:6 equilibrium mixture of the two; this isomerization does not occur with LiCl. The Cl-atoms of both 2a , b and 3a , b and of 2c may reductively be removed with Zn(Cu) in AcOH/pyridine to afford the alkylcyclobutenones 4a-c . Without pyridine, this reduction gives ca. 1:1 mixtures of the double-bond isomers 4 and 5 in low yields. The cyclobutenones 2c and 4c may be deuterated by CD₃COOD in the presence of pyridine. D -Atom is introduced into 2c at C(4) and at C(γ), and into 4c at C(2) and C(4). A mechanism for this deuteration is considered, which does not involve a cyclobutadienolate 7 , but rather a cyclobutenolate of type 8 . The reductions of 2 and 3 to 4 might also pass through the same type of intermediate 8 .     

Selektivierung geringer Mengen Kupfer mit Polyäthylenimin-Zellulose

Zusammenfassung Polyäthyleniminzellulosen sorbieren Cu²⁺ durch koordinative Bindung als Zentralion des sekundären Stickstoffs des Polyäthylenimins im P_H-Bereich 3,5 bis 4,5 selektiv aus verd. Lösungen. 10g Kupfer können von 10⁵fachen Überschüssen anderer Übergangsmetalle separiert, mit verd. Salzsäure eluiert und mit Diäthyldithiocarbamat photometrisch bestimmt werden. Das Verfahren eignet sich zur Erfassung von 0,001% Kupfer in Zink, Mangan, Kobalt, Nickel, Cadmium und Aluminium sowie aus Lösungen, deren Kupfergehalt 0,02 ppm beträgt.

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Selectivation of small amounts of copper with polyethyleneimine-cellulose

Summary Polyethyleneimine celluloses selectively sorb Cu²⁺ from dilute solutions through coordinative bonding as central ion of the secondary nitrogen of polyethyleneimine in the p_H-range of 3.5–4.5. 10g of copper may be separated from 10₅-fold excesses of other transition metals, then eluted with dilute hydrochloric acid and determined photometrically with diethyldithiocarbamate. The method is suitable for determining 0.001% copper in zinc, manganese, cobalt, nickel, cadmium, and aluminium as well as in solutions whose coppercontent is 0.02 ppm.

     

Beitrag zur Analyse von Stibin

Zusammenfassung Es wird ein Verfahren zur Bestimmung von Stibin beschrieben, das sich sowohl zur Analyse von SbH₃ in organischen Lösungsmitteln als auch zur Bestimmung von flüssigem oder festem SbH₃ eignet. Hierbei wird das Stibin mit überschüssigem Brom zu Sb^V oxydiert, danach mit SO₂ zu Sb^III reduziert und dieses oxydimetrisch mit Jod oder Bromat titriert.

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Summary A method is proposed for the determination of stibine, applicable to its solutions in organic solvents and also to the solvent-free liquid or solid substance. The procedure involves oxidation of SbH₃ with an excess of bromine to Sb^V, reduction to Sb^III with SO₂, and oxidimetric titration of the trivalent antimony with iodine or bromate.

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Herrn Professor Dr. C. Mahr zum 65. Geburtstag gewidmet.