Bemerkungen zur Synthese von 5-Amino-m-xylol-2-sulfonsäure und 5-Amino-m-xylol-4-sulfonsäure

Some comments on the syntheses of 5-amino-m-xylene-2-sulfonic acid and 5-amino-m-xylene-4-sulfonic acid Treatment of 5-amino-m-xylene ( 1 ) with oleum led to a 55:45 mixture of 5-amino-m-xylene-2-sulfonic acid ( 2 ) and 5-amino-m-xylene-4-sulfonic acid ( 3 ). The structure of both isomers was proven by reaction of sulfur dioxide with the diazonium chlorides derived from 2-amino-5-nitro-m-xylene ( 5 ) and 4-amino-5-nitro-m-xylene ( 8 ) giving 5-nitro-m-xylene-2-sulfonyl chloride ( 6 ) and 5-nitro-m-xylene-4-sulfonyl chloride ( 9 ) respectively, followed by hydrolyses to the corresponding sulfonic acids 7 and 10 , and final Béchamp reductions. The sulfonic acid 2 was also prepared by sulfonation of 5-acetylamino-m-xylene ( 4 ) to 5-acetylamino-m-xylene-2-sulfonic acid ( 11 ) and subsequent hydrolysis. A further procedure for the synthesis of 3 was sulfonation of 5-amino-2-chloro-m-xylene ( 12 ) – prepared by Béchamp reduction of 2-chloro-5-nitro-m-xylene ( 13 ) – or of 5-amino-2-bromo-m-xylene ( 15 ) – prepared by bromination of 4 and subsequent hydrolysis – to 5-amino-2-chloro-m-xylene-4-sulfonic acid ( 16 ) and 5-amino-2-bromo-m-xylene-4-sulfonic acid ( 17 ) respectively, followed by hydrogenolysis.     

Notiz zur Synthese von rac. cis- und trans-2-Nor-abscisinsäure

Note on the synthesis of rac. cis- and trans-nor-abscisic acid The synthesis of the 2-nor-analogues of cis- and trans-abscicic acid is described.     

Die Koordinationszahl von Lanthaniden: Thermodynamik der LnIIIEDTA-Mischkomplexe mit den Anionen der 8-Hydroxychinolin-5-sulfonsäure,Iminodiessigsäure und Nitrilotriessigsäure

The values of ΔG, ΔH and ΔS for the formation of the mixed 1:1:1 lanthanide EDTA complexes with the anions of 8-hydroxyquinoline-5-sulfonic acid, iminodiacetic acid and nitrilotriacetic acid were determined by pH-titrations and a direct calorimetric method. These thermodynamic data are discussed and compared with those for the formation of the Ln(III)EDTA complexes. Contrary to current opinion it is concluded that all trivalent lanthanide aquoions have the same coordination number in dilute solution. However, in the series of the lanthanide EDTA complexes the coordination number changes between Sm and Tb. In this region, equilibria occur between two types of EDTA complexes with different numbers of coordinated water molecules: The corresponding equilibrium constants could be evaluated. The coordination number changes also in many other Ln complexes along the lanthanide series, and similar equilibria occur.     

Synthese und Kristallstruktur der Hydroxy-lactone von 6-Methyl-2-propionyl- und 3-Methyl-2-propionylbenzoesäure

The isomers 6-methyl-2-propionyl- and 3-methyl-2-propionylbenzoic acid were synthesized and separated by DCC (droplet counter-current) chromatography. The crystal structure analyses showed that these compounds are hydroxylactones in the solid state.     

Beitrag zur Analytik und Synthese von 3-Hydroxy-4-oxocarotinoiden

Contribution to the Analytical Separation and the Synthesis of 3-Hydroxy-4-oxocarotenoids (3RS,3′RS)-Astaxanthin (= 3,3′-dihydroxy-β,β-carotene-4,4′-dione, 1:1-mixture of racemate and meso-form; 1 ) can be separated into its optical isomers (3S,3′S)- 1a , (3R,3′R)- 1b and meso-(3R,3′S)- 1c via the corresponding diastereomeric di-(?)-camphanates. Some aspects of the configurational stability of astaxanthin are discussed. - HPLC. analysis of the (?)-camphanates of 3-hydroxy-4-oxocarotenoids provides, in suitable cases and supported by spectroscopic data, an analytical method for the simultaneous determination of constitution and chirality.     

Inter- und intramolekulare Umlagerung der Sulfogruppe in 2-Naphtol-1-sulfonsäure

The isomerisation of 2-naphthol-1-sulfonic acid (potassium salt) into 2-naphthol-6-sulfonic acid has been studied using labelled sulfuric acid (H₂³⁵SO₄). In 40 to 50% aqueous sulfric acid the reaction takes place exclusively by an intermolecular mechanism (protio-desulfonation and resulfonation). In glacial acetic acid, in the presence of an excess of sulfuric acid, the rearrangement is partly intramolecular. With an equimolar amount of sulfuric acid the rearrangement is completely intramolecular. This reaction is first order with respect to 2-naphthol-1-sulfonic acid and zeroth order with respect to excess of sulfuric acid. A mechanism for the reaction is proposed.     

Synthese von (+)-Abscisinsäure

Synthesis of (+)-Abscisic Acid . Starting from (4S)-4-hydroxy-2,6,6-trimethylcyclohex-2-enone ( 2 ), a short synthesis of the natural (+)-abscisic acid ((+)- 1 ) has been accomplished.     

Synthese von 5-Methyl-3-oxa-A-nor-5β-cholestan und 3-Oxa-Δ4-cholesten-2-on

2, 3-seco-Δ⁴-Cholestene-2, 3-dicarboxylic acid ( 5 ) was prepared in 30% yield from 2-hydroxymethylene-Δ⁴-cholestene-3-one ( 1 ) by ozonolysis under special conditions. Pyrolysis of the pure di-acid 5 gave A-nor-Δ³⁽⁵⁾-cholestene-2-one ( 6 ), the anhydride 2 and 5-methyl-3-oxa-A-nor-5β-cholestane-2-one ( 8 ). Pyrolysis of amorphous acidic material obtained by the ozonolysis of 1 yielded the enol-lactones 7 and 9 as additional products. LiA1H₄-reduction of the γ-lactone 8 gave the diol 10 , which was transformed into 5-methyl-3-oxa-A-nor-5β-cholestane ( 13 ) by treatment with tosyl chloride in pyridine.     

Synthese und Eigenschaften von 6-Desoxy-6-halogen-Derivaten der L-Ascorbinsäure

Synthesis and Properties of 6-Deoxy-6-halogeno-Derivatives of L -Ascorbic Acid 6-Deoxy-6-chloro-, -6-bromo-, -6-iodo- and -6-fluoro derivatives of L -ascorbic acid have been synthesized and characterized. The physiological properties of the chloro derivative have been investigated. It shows a high antiscurvy activity. The chloro- and bromo-derivatives have been reduced to the corresponding deoxy compound, which is an interesting chiral intermediate for the preparation of rare ω-deoxy sugars.     

Synthese von 4-Trichlorsilylmethylbenzonitril und 4-(2-Trichlorsilyläthyl)pyridin zur Oberflächenmodifikation von Zinndioxid

Synthesis of 4-Trichlorosilylmethylbenzonitrile and 4-(2-Trichlorosilylethyl)pyridine for Surface Modification of Tin Dioxide We describe the synthesis of 4-(trichlorosilylmethyl)benzonitrile and 4-(2-trichlorosilylethyl)pyridine, starting from 4-(bromomethyl)benzonitrile and trichlorosilane or vinylpyridine and trichlorosilane. Trimethoxysilanes are obtained by reaction of the trichlorosilyl compounds with methyl orthoformate. 4-(Trichlorosilylmethyl)benzonitrile and 4-(2-trichlorosilylethyl)pyridine are used to modify the surface of tin dioxide.     

Synthese von phenoxygruppenhaltigen Derivaten der Methandiphosphonsäure

Synthesis of Phenoxy Derivatives of Methanediphosphonic Acid Derivatives of the methanediphosphonic acid containing different numbers of phenoxy groups were prepared by Michaelis-Arbusov reaction of iodomethane phosphonic acid esters with phosphorous acid esters and by reaction of methane diphosphonic acid tetrachlorid with sodium phenolate. The obtained products were investigated by means of n.m.r. spectroscopy.