Manfred Schubert-Zsilavecz

Structure Investigation and Proton and Carbon-13 Assignments of Digitonin and Cholesterol using Multidimensional NMR Techniques

Digitonin, a spirostanolglycoside from the seeds of Digitalis purpurea L., is a highly haemolytically active saponin. This effect is considered to be based on complex formation between cholesterin and digitonin. Against the background of investigations concerning the interaction between glycosides and membrane components, and the determination of the structure of the digitonin–cholesterol complex, a detailed NMR spectroscopic investigation of thecomplex‐forming compounds was carried out. Assignment of the 1H and 13C spectra of digitonin was made by using one‐ and two‐dimensional NMR techniques (1D TOCSY, 2D TOCSY, HMQC and HMBC); 3D TOCSY–ROESY, 1D ROESY and HMBC experiments provided information about the sequence of the oligosaccharide chain and the position of glycosidations. The precise analysis of the COSY, HMQC und HMBC spectra made the assignment of all proton resonance signals of cholesterol possible for the first time.

2H-Isoindol-4,7-dione durch Addition von Azomethinyliden an 1,4-Benzochinone

SummaryA new approach to the synthesis of 2H-isoindole-4,7-diones is described. Heating α-amino acids with carbonyl compounds generates azomethine ylides through the elimination of water and carbon dioxide. The ylides were captured by quinones forming 2H-isoindole-4,7-diones, 2,3,3a,7a-tetrahydro-1H-isoindole-4,7-diones and 2,3-dihydro-1H-pyrrolo[2,1-a]isoindole-6,9-diones. The structures were established on the basis of spectroscopy (NMR, mass).

Coumarins from Peucedanum ostruthium

Abstract Two new coumarins, 6-(3-carboxybut-2-enyl)-7-hydroxycoumarin and the 3′-acetate of oxypeucedanin hydrate, were isolated from the roots of Peucedanum ostruthium , and their structures were established mainly by mass spectrometry and 2D NMR techniques.

1,2-Oxazoline durch Addition von Trimethylbenzonitriloxid an 2-Hydroxyethylamino-1,4-benzochinone und deren Chinolderivate

SummaryAddition of trimethylbenzonitril oxide to 2-hydroxyethylamino-1,4-quinones and 3,4-dihydro-4-alkyl-8a-methoxy-2H-1,4-benzoxazin-6(8aH)-ones leads to 7,8,9a,9b-tetrahydro-3aH-1,2-oxazolo[4,5-h]-1,4-benzoxazin-4(6H)-ones. In order to determine constitution and conformation of the addition products an NMR-spectroscopic analysis and an X-ray crystal structure analysis of 6-benzyl-9a-hydroxy-3-mesityl-7,8,9a,9b-tetrahydro-3aH-1,2-oxazolo[4,5-h]-31,4-benzoxazin-4-(6H)-one3a were carried out at room temperature: C25H26N2O4,Mr=418.49, monoclinic, P21/n,a=13.716(6),b=19.993(6),c=15.348(6) Å, β = 98.55(4)°,V=4162(1)Å3,Z=8,dx=1.336g/cm3,R=6.77%,Rw=4.55% (2994 observables, 560 parameters).

1,2-Thiazole durch Ringtransformation von 2H-Thiopyran-2-thionen

SummaryAminolyses of 4-dialkylamino-2-methylthiothiopyranes halides with ammonia leads to 4-amino-2-dialkylaminothiopyranylium halides. On treatment with alkali these products are hydrolyzed to N,N-dialkyl-3-amino-2,4-hexadienthioamides, which react with peroxide under oxidative cyclization to 5-dialkylamino-1,2-thiazoles. In order to determine the structures of the unsaturated thioamides and isothiazoles13C-NMR-spectroscopic analysis and a single crystal X-ray structure analysis of 5-dimethylamino-3-(2-methyl-1-propenyl)-1,2-thiazole (6 a) at 100K were carried out: C9H14N2S,Mr=182.28, monoclinic, P 21/a,a=11.622(2),b=6.303 (1),c=13.678(2), β=104.49(3)°,V=970.1(3)Å3,Z=4,dx=1.248 g/cm3, μ=27.0 mm−1,R=4.93%,Rw=4.84% (1 672 observations, 157 parameters).

Elektrochemische Eigenschaften von 6-Methoxy-2,5-dimethyl-2H-isoindol-4,7-dion, einem antimikrobiell wirksamen Alkaloid ausReniera-Arten

SummaryTo determine the electronaffinity of 6-methoxy-2,5-dimethyl-2H-isoindole-4,7-dione — the first naturally-occurring isoindole alkaloid — the peak potential was measured by DPP.

Zur Umsetzung von 3,4-Dihydro-8a-methoxy-2H-1,4-benzoxazin-6(8aH)-onen mit Diazoalkanen, 1. Mitt.

Summary3,4-Dihydro-8a-methoxy-2H-1,4-benzoxazin-6(8aH)-ones — quinol derivatives of 2-hydroxyethylamino-1,4-benzoquinones — react with diazoalkanes to yield 2,3,9a,9b-Tetrahydro-9H-pyrazolo[3,4-h]-1,4-benzoxazin-6(6aH)-ones (3). Their structures were established on basis of NMR-techniques including two-dimensional experiments. The orientation phenomena of the reaction is discussed.

SYNTHESE UND POLAROGRAPHISCHES VERHALTEN VON 2H-ISOINDOL-4,7-DIONEN

Summary2-Phenylthio-1,4-benzoquinone (1 a) reacts with azomethine ylide AY-A to give 2-methyl-5-phenylthio-2H-isoindole-4,7-dione (4 f). With 2-(N-methylanilino)-5-methyl-1,4-benzoquinone (1 b), the azomethine ylide AY-B undergoes cycloaddition to yield an inseparable mixture of 5a-methyl-8-(N-methylanilino)-2,3,5,5a,9a,9b-hexahydro-pyrrolo[2,1-a]1H-isoindole-6,9-dione (5 bI) and 9a-methyl-7-(N-methylanilino)-2,3,5,5a,9a,9b-hexahydropyrrolo[2,1-a]1H-isoindole-6,9-dione (5 bII). The structures of5 bI and5 bII were established on basis of two-dimensional-NMR-techniques. The mechanism of the cycloaddition of azomethine ylides to 1,4-quinones was studied on basis of cyclovoltammetric investigations. To determine the electron affinity of the isoindoledione derivatives4 a–f and5 a–b the peak potentials were measured by differential pulse polarography (DPP).

DETERMINATION OF NISOLDIPINE IN FILM TABLETS BY DIFFERENTIAL PULSE POLAROGRAPHY

SummaryA differential pulse polarographic (DPP) method was developed for the determination of nisoldipine in Baymycard® film tablets without interference from excipients. Nisoldipine is reduced at the dropping mercury electrode in a single, irreversible peak. Linearity between the nisoldipine concentration and the peak height was observed in the 5·10−4–10−7M concentration range. The detection limit is 22 ng/ml. The analysis of a series of 10 Baymycard® 5 mg film tablets showed a standard deviation of ±0.115 mg and aSrel of ±2.30%, respectively.ZusammenfassungEine Bestimmung von Nisoldipin in Baymycard® Filmtabletten mittels differentieller Pulspolarographie (DPP) wurde entwickelt, die keine Störungen durch Tablettenhilfsstoffe aufweist. Nisoldipin wird an der tropfenden Quecksilberelektrode in einem einzigen, irreversiblen Peak reduziert. Linearität zwischen Nisoldipinkonzentration und Peakhöhe wurde im Konzentrationsbereich von 5·10−4–10−7M festgestellt. Die Bestimmungsgrenze beträgt 22 ng/ml. Die Analyse einer Serie von 10 Baymycard® 5 mg Filmtabletten ergab eine Standardabweichung von ±0.115 mg, dies entspricht einerSrel von ±2.30%.

REACTIONS OF HYDROXYETHYLAMINO-1,4-BENZOQUINONES WITH 2,4,6-TRIMETHYLBENZONITRILE OXIDE. II

Summary3,4,9a,9b-Tetrahydro-2H-1,2-oxazolo[5,4-h]1,4-benzoxazin-6(6aH)-ons5a–c were obtained by the reaction of hydroxyethylamino-1,4-benzoquinones2a–c with nitrile oxide3. The structures of the cycloadducts were elucidated NMR techniques including inverse longe-range13C,1H-experiments and homonuclear NOE difference spectroscopy.ZusammenfassungBei der Reaktion von Hydroxyethylamino-1,4-benzochinonen2a–c mit dem Nitriloxid3 werden 3,4,9a,9b-Tetrahydro-2H-1,2-oxazolo[5,4-h]1,4-benzoxazin-6(6aH)-one5 erhalten. Deren Strukturen wurden NMR-spektroskopisch — unter Einbeziehung inverser long-range13C,1H-Experimente und NOE-Differenz-Spektroskopie — aufgeklärt.