Synthese von N-Methyl- und N,N-Dimethylmerucathin sowie von N-Methyl- und N,N-Dimethylpseudomerucathin aus L-Alanin

Synthesis of N-Methyl- and N,N-Dimethylmerucathine and of N-Methyl- and N,N--Dimethylpseudomerucathine Starting from L -Alanine Starting form L -alanine, N-methylmerucathine (= (3R,4S)-4-(methylamino)1-phenyl-1-penten-3-ol; (3R,4S,)- 6 ), N,N-dimethylmerucathine (= (3R,4S)-4-(dimethylamino)-1-phenyl-1-penten-3-ol; (3R,4S)- 9 ), N-methylpseudomerucathine (= (3S,4S)-4-(methylamino)-1-phenyl-1-penten-3-01; (3S,4S)-6), and N,N-dimethylpseudomerucathine (= (3S,4S)-4-(dimethylamino)-1-phenyl-1-penten-3-ol; (3S,4S)- 9 ) were synthesized. The four compounds were analyzed by HPLC and compared with a natural khat extract.     

Calculation of the deuteron quadrupole relaxation rate in a mixture of water and dimethyl sulfoxide

An approach is presented that allows NMR relaxation rates to be determined for a complex mixture, and it is applied to a dimethyl sulfoxide/water solution. This approach is novel for such systems, having only been used for simple systems such as atomic liquids or atomic ions in liquids until now. It involves use of a predetermined, quantum mechanical, multidimensional property surface in a simulation. The results are used in conjunction with the simulated rotational correlation time to calculate the deuteron quadrupole coupling constant (DQCC), in an analogous approach to the one used by experimentalists, and to examine the surprising experimental findings for the composition dependence of the DQCC in the dimethyl sulfoxide/water mixture. Experiments have suggested that the DQCC for a mixture of 5% dimethyl sulfoxide in water is close to the DQCC of ice, whereas its value increases to a value close to the gas value with further dilution.(1) The results are further critically analyzed using combinations of different experimental and theoretical results from the literature.     

17O-NMR-spectroscopy as a tool for stereochemical analysis — Application to a diterpene-derivative

Summary Treatment of abietic acid methylester with Hg(OAc)₂/MeOH produces a dimethoxy derivative. The determination of the configuration at C-7 of this product by means of 1D- and 2D-NMR-spectroscopic methods is described. The results are verified by application of¹⁷O-NMR spectroscopy and comparison with well-established stereochemical dependencies of¹⁷O chemical shifts.

---

¹⁷O-NMR-Spectroskopie zur stereochemischen Analyse. Anwendung auf ein Diterpen-Derivat

Zusammenfassung Umsetzung von Abietinsäuremethylester mit Hg(OAc)₂/MeOH führt zu einem Dimethoxyderivat. Die Bestimmung der Konfiguration am Zentrum C-7 erfolgt durch Anwendung von 1D- und 2D-NMR-Methoden. Die Resultate konnten durch¹⁷O-NMR-Spektroskopie aufgrund der bekannten stereochemischen Verschiebungsabhängigkeit bestätigt werden.

     

Synthese von einigen 2H-Pyran-2-on-Derivaten

The Synthesis of Some 2H-Pyran-2-one Derivatives Derivatives of 6-unsubstituted 2H-pyran-2-one have been synthesized by several different methods. The 4-chloro-2H-pyran-2-one ( 9 ) is the most important, since it serves as starting material for the synthesis of different 4-substituted 2H-pyran-2-ones (Scheme 2). Also described are simple transformations of cumalic-acid derivatives producing 5-(2,2-dichlorovinyl)-2H-pyran-2-one ( 23 ), 2-oxo-2H-pyran-2-carbonitrile ( 26 ), and 4,5-bis(trifluoromethyl)-2H-pyran-2-one ( 32 ) (Scheme 3 and 4).     

1H-and 13C-NMR Investigation of Pentafulvenes

¹H- and ¹³C-NMR spectra of a series of 6-(p-X-phenyl)pentafulvenes 1 – 9 as well as of 6-R-substituted and 6,6-R¹,R²-disubstituted pentafulvenes 10 – 23 have been analysed. It turns out that the π-system of pentafulvenes is an attractive probe for the investigation of electronic substituent effects. Changes of vicinal H,H-coupling constants with increasing electron-donating capacity of the substituents X and R are interpreted in terms of an increasing π delocalisation in the 5-membered ring, and linear correlations of Hammett Substituent constants σ or MNDO-calculated C–C bond lengths and ³J values are observed. On the other hand, a systematic high-field shift of ₁₃C chemical shifts of the ring C-atoms is induced by electron-releasing substituents R and X, which decreases in the series C(5) > C(2)/C(3) > C(1)/C(4), and which mainly reflects changes in π-charge density.     

Synthesis,polarography and herbicidal activity of quaternary salts of 2-(4-pyridyl)-1,3,5-triazines, 5-(4-pyridyl)pyrimidine, 2-(4-pyridyl)pyrimidine and related compounds

2-(4-Pyridyl)-1,3,5-triazine, 2-(4-pyridyl)-4-methyl-1,3,5-triazine, 2-(4-pyridyl)-4,6-dimethyl-1,3,5-triazine and 2-(4-pyridyl)pyrimidine have been prepared by modification of established triazine and pyrimidine syntheses. These compounds and some of their relatives have been converted to quaternary pyridinium salts. The polarographic reduction potentials of the salts in aqueous solution are pH dependent. The activity of the salts as post-emergent herbicides is reported.     

Synthesis and NMR Spectroscopic Investigation of a Macrocyclic Diphosphine Ligand and its nickel(II) and palladium(II) complexes

The preparation of a macrocyclic diphosphine ligand 5 incorporating a binaphthyl unit and its Ni^II and Pd^II complexes, 6 and 7 , is described. A complete assignment of ¹H,- ¹³C-, and ³¹P-NMR data on the basis of 2D NMR spectroscopy (¹H, ¹H-, ¹³C, ¹H-, ³¹P, ¹H-, ³¹P, ¹³C-COSY) was possible for 5 , and also – in part – for 6 and 7 .     

17O NMR studies on (E)-3-arylidenechromanone and -flavanone derivatives

¹⁷O NMR data for some 3-arylidenechromanones and -flavanones are discussed in terms of mesomeric and steric substituent interactions. The transmission of long-range substituent effects was studied. ¹⁷O NMR chemical shifts were correlated with Hammett σ_p⁺ values for 4′-substituted derivatives. Copyright © 2001 John Wiley & Sons, Ltd.