F. Holger Försterling

Copper(I) pseudohalide complexes with 4,6-dimethylpyrimidine-2(1H)-thione and triphenylphosphane as ligands. The X-ray crystal structures of [Cu(N3)(dmpymtH)(PPh3)2] and [Cu(NCS)(dmpymtH)(PPh3)2]

Abstract The preparation of mixed-ligand copper(I) coordination compounds containing pseudohalides (azide and thiocyanate), 4,6-dimethylpyrimidine-2(1H)-thione (dmpymtH), and triphenylphosphane is described. The crystalline and molecular structure of [Cu(N3)(dmpymtH)(PPh3)2] (2) and [Cu(NCS)(dmpymtH)(PPh3)2] (3) have been determined by X-ray diffraction methods. The copper atom has a tetra-coordinate CuNP2S chromophore with distorted tetrahedral coordination in both complexes. Vibrational and 1H, 13C, 31P NMR spectra of the complexes are discussed and related to the structures.

Study of the Cis to Trans Isomerization of 1-Phenyl-2,3-disubstituted Tetrahydro-β-carbolines at C(1). Evidence for the Carbocation-Mediated Mechanism

The present study was undertaken to shed light on the mechanism of the epimerization of cis-1,2,3-trisubstituted tetrahydro-beta-carbolines into the trans isomers via a potential carbocationic intermediate at C(1). In order to study the pathway involved in C(1)-N(2) bond cleavage, the electronic character of the carbon atom at C-1 was altered by substitution of electron-rich and electron-poor phenyl rings at this position. This provided direct evidence of the effects of charge at the proposed site of the carbocationic intermediate. In this regard, a diverse set of 1-(phenyl substituted)-2-benzyl-3-ethoxycarbonyl-1,2,3,4-tetrahydro-beta-carbolines has been synthesized via the Pictet-Spengler reaction by condensation of l-tryptophan derivatives with electron-poor and electron-rich aromatic aldehydes. The epimers involved in the isomerization mechanism were investigated by dynamic (1)H and (13)C NMR spectroscopic and X-ray crystallographic analyses. The kinetic studies, which involved conversion of cis diastereomers into their trans counterparts, were carried out in dilute TFA/CH(2)Cl(2). The 1-(4-methoxyphenyl) cis diastereomer epimerized at a much faster rate into the corresponding trans diastereomer than the related 1-(4-nitrophenyl) cis diastereomer epimerized. These observations provide support for the carbocationic intermediate in the C(1)-N(2) scission process. The understanding of this epimerization process is of importance when Pictet-Spengler reactions are carried out under acidic conditions during the synthesis of indole alkaloids.

A study of the structure-activity relationship of GABAA-benzodiazepine receptor bivalent ligands by conformational analysis with low temperature NMR and X-ray analysis

The stable conformations of GABA(A)-benzodiazepine receptor bivalent ligands were determined by low temperature NMR spectroscopy and confirmed by single crystal X-ray analysis. The stable conformations in solution correlated well with those in the solid state. The linear conformation was important for these dimers to access the binding site and exhibit potent in vitro affinity and was illustrated for alpha5 subtype selective ligands. Bivalent ligands with an oxygen-containing linker folded back upon themselves both in solution and the solid state. Dimers which are folded do not bind to Bz receptors.

Synthesis of some substituted adamantane-2,4-diones from 4, 4-disubstituted cyclohexanone enamines and methacryloyl chloride

The reaction of methacryloyl chloride with the morpholine enamine 4a derived from 4-acetyl-4-isopropenylcyclo-hexanone 3a gave 4,6-anti-6-hydroxy-5,6-dimethyl-7-isopropenyladamantane-2,4-dione 6a and 4,6-syn-6-hydroxy-5,6-dimethyl-7-isopropenyladamantane-2, 4-dione 7a as racemates epimeric at 6-C. Comparable results were found for the corresponding phenyl and benzyl substituted cyclohexanones 3b and 3c. In the case of the methyl-substituted cyclohexanone 3d 4,6- anti-alcohol 7d was isolated in pure form.

Synthesis of substituted tricyclo[5.3.1.04,9]undecan-2,6-dione from 4,4-disubstituted cyclohexanone enamines and methacryloyl chloride

Abstract Morpholine enamines 4‐acetyl‐4‐methyl‐1‐morpholinocyclohexene 4a, 4‐acetyl‐4‐phenyl‐1‐morpholinocyclohexene 4b, and 4‐acetyl‐4‐isopropenyl‐1‐morpholinocyclohexene 4c react with methacryloyl chloride to give 1,7‐dimethyl‐4(N‐morpholino) tricyclo[5.3.1.04,9]undecan‐2,6‐dione 9a , 1‐phenyl‐7‐methyl‐4(N‐morpholino) tricyclo[5.3.1.04,9]undecan‐2,6‐dione 9b , and 1‐ispropenyl‐7‐methyl‐4(N‐morpholino) tricyclo[5.3.1.04,9]undecan‐2,6‐dione 9c respectively, along with the corresponding substituted adamandane‐2,4‐diones.