Zur Synthese. von D-Glucopyrano-(cis-2′, 1′-c)-l,2,3,4-tetrahydro-isochinolinen

By a modified POMERANZ-FRITSCH -reaction substituted D-glucopyrano-1,2,3,4-tetrahydro-isoquinolines have been obtained in high yields from substituted N-benzyl-D-glucosamines. The structure of the products has been confirmed by N.M.R. spectroscopy.     

Zum Einfluß von Zusätzen auf die Hydratation von Tricalciumsilicat (Ca3SiO5)

On the Influence of Admixtures on the Hydration of Tricalcium Silicate (Ca₃SiO₅) The influence of several compounds (alcohols, ketones, organic acids and the ir salts, cation exchange resin) on the hydration of tricalcium silicate was investigated by means of differential calorimetric analysis (DCA). The acceleration and retardation of this reaction found in these experiments are discussed on the basis of Ca(OH)₂ solubility, the pH of the solution and the rate of conversion of a C? S? H rich in CaO into a C? S? H poor in CaO at the surface of the C₃S grains.     

Theoretical and experimental study on cyclic 6-methyl-2,3,4-tris(hydroxymethyl)pyridin-5-ol acetonides

Methods for the preparation of three cyclic 2,3,4-tris(hydroxymethyl)-6-methylpyridin-5-ol acetonides have been developed by variation of the reaction conditions. The six-membered acetonide turned out to be thermodynamically more stable than the seven-membered acetonide and bis-acetonide. The experimental data were consistent with the results of quantum-chemical calculations. The structure of the isolated compounds was proved by X-ray analysis.     

Zur Wirkung von Citronensäure auf die Hydratation von Tricalciumsilicat (Ca3SiO5)

The Influence of Citric Acid on the Hydration of Tricalcium Silicate (Ca₃SiO₅) The influence of citric acid on the hydration of tricalcium silicate was investigated. The strong retarding effect of this acid is discussed on the basis of Ca(OH)₂ solubility, the formation of a protective layer at the surface of Ca₃SiO₅ and an inhibition of the crystallization of calcium hydroxide.     

Synthese von (+)-(5S, 6S)-Azafrin-methylester; absolute Konfiguration von Aeginetinsäure and von weiteren vicinalen Apocarotin-diolen

Synthesis of (+)-(5S, 6S)-Azafrin Methyl Ester; Absolute Configuration of Aeginetic Acid and of Further Vicinal Apocarotenediols We describe the synthesis of a series of optically active vicinal apo-β-carotenediols. Thus, starting from (+)-(5S, 6S)-5,6-dihydroxy-5,6-dihydro-β-ionone ( 2 ) we have prepared the (Z/E)-isomeric (+)-C₁₅-esters 7 and 8 , the (+)-retinoic derivatives 14 , 15 , 18 , 19 and (+)-methyl azafrinate ( 22 ), the enantiomer of the naturally occur-ring compound (s. Scheme 1). Our synthesis also establishes the absolute configura-tion of aeginetic acid ( 24 ), aeginetoside ( 25 ) and aeginetin ( 26 ), compounds isolated from the root parasite Aeginetia indica by Indian and Japanese workers (s. Scheme 2). The presented synthesis of optically active methyl azafrinate confirms our previous assignment [14] of the absolute configuration of azafrin ( 1a ), which was based on degradative evidence.     

Die Kristallstruktur von [BeCl2(15‐Krone‐5)]

Crystal Structure of [BeCl₂(15‐Crown‐5)] Single crystals of [BeCl₂(15‐crown‐5)] ( 1 ) were obtained from dichloromethane solutions of BeCl₂ in the presence of the equivalent amount of 15‐crown‐5 and characterized by IR spectroscopy and X‐ray diffraction. Space group P2₁/c, Z = 4, lattice dimensions at 100 K: a = 1036.2(1), b = 1071.1(1), c = 1360.1(1) pm, β = 109.86(1)°, R₁ = 0.0225. The structure determination shows no disorder, all hydrogen positions were refined isotropically. The results are in contrast to the previously reported crystal structure determination in the space group P2₁nb. The beryllium atom of 1 forms a BeO₂C₂ five‐membered heterocycle with terminal chlorine atoms to give a distorted tetrahedral coordination with distances Be–O 166.5(2), 169.9(2) pm, and Be–Cl 195.8(2), 197.8(2) pm. The structural results are in good agreement with DFT calculations on B3LYP/6‐311+G** level.