Synthesis of cyclic dipeptide templates, their incorporation into peptides and studies on their conformational and biological properties.

This study investigated the diastereoselective synthesis of three dipeptide templates 1, 2 and 3, which may be regarded as conformationally restricted analogs of H-Gly-Xaa-OH, in which Xaa constitutes an aromatic amino acid. Bond formation between alpha-C of Gly and the aromatic moiety was achieved by proton-catalyzed intramolecular electrophilic aromatic substitution. The absolute configuration of the dipeptide templates was determined by single-crystal X-ray crystallography or by nuclear Overhauser enhancement measurements. A protective group strategy was elaborated to allow their incorporation into peptide sequences by liquid phase as well as by solid-phase peptide synthesis. The templates were used to generate an enkephalin analog 15, a modified peptidic neurokinin antagonist 20 and two dermorphin derivatives (24 and 33). Molecular dynamic simulations with 15 and 20 revealed the preference for a turn-like motif for 15. The biological activity, as investigated by respective receptor binding and functional assays, was strongly diminished with all four derivatives, indicating that their receptor-relevant molecular geometries lie outside the examined conformational space.

Synthesis of a new dipeptide template, its X-ray structure, and modeling studies on its conformational features.

The diastereoselective synthesis is reported of a dipeptide template which is closely related to H-Gly-Trp-OH. Intramolecular bond formation between alpha-C of Gly and ring position 2 of the Trp unit has been achieved by a Pictet-Spengler-type electrophilic aromatic substitution. The absolute configuration of the N-Moc protected dipeptide template 9.2H2O was determined by single-crystal X-ray crystallography and found to be (2S,5S). The cis orientation of the amino and carboxy termini prompted us to investigate the potential of 9 as a beta-turn mimic. MD calculations on the model pseudopeptide Ac-Ala-Gly-Trp-Ala-NHMe 11 suggest that an unusually tight turn should be favoured rather than a beta-turn. The proper protective situation as a pre-requisite for the incorporation of the template into a peptide has been established, and comments about its chemical properties are given.

Synthesis of the bronchospasmolytic agent flutropium bromide and of some homologous and configuration isomeric compounds.

A technically practicable synthesis of unknown N-beta-fluoroalkyl-substituted benzilic acid nortropine esters, among them (8r)-8-(2-fluoroethyl)-3 alpha-hydroxy-1 alpha H, 5 alpha H-tropanium bromide benzilic acid ester (flutropium bromide, Ba 598 BR), and their configuration isomeric quaternary salts via benzilic acid imidazolide is described. The quaternization which takes place with sufficiently high stereo-selectivity leads to configuration isomers which differ not only in their physico-chemical properties but also in their profile of pharmacological action.

Metabolic fate of [14C]-brotizolam in the rat, dog, monkey and man.

The metabolism of brotizolam (2-bromo-4-(2-chlorophenyl)-9-methyl-6H-thieno [3,2-f]-1,2,4-triazolo[4,3-a]-1,4-diazepine, We 941, Lendormin) was studied in the bile of the rat and in the urine of the dog, rhesus monkey and man using 14C-labeled substance. Concentration, fractionation and purification of the metabolites were performed using thin layer chromatography, column chromatography or high pressure liquid chromatography. Metabolites were structurally characterized by thin layer chromatography, high pressure liquid chromatography, mass spectrometry and nuclear magnetic resonance spectrometry using reference compounds. Hydroxylation at different sites of the brotizolam molecule and subsequent conjugation were the metabolic pathways preferred by far in the species studied. Unchanged brotizolam was excreted in minute amounts only, if at all. In man and monkey We 964 (brotizolam hydroxylated in the methyl group) and We 1061 (brotizolam hydroxylated in the diazepine ring) represented the main metabolites. In the rat, the main metabolites were We 1061 and a brotizolam hydroxylated in the phenyl ring. The main metabolites found in the dog were We 964 and We 1064, an isomeric compound of We 1061. Since We 1061 is irreversibly transformed in an alkaline medium to We 1064, the latter could be formed due to the clean-up processes. Thus, in the dog also We 1061 was probably the metabolite which was actually excreted renally. The proposed structures of minor metabolites are presented.

[Synthesis of anticholinergically active N-alkylnorscopolamines and their quaternary salts with special consideration of the bronchospasmolytic (-)-N-ethylnorscopolamine methobromide (Ba 253 BR)]. / Synthese von anticholinerg wirksamen N-Alkylnorscopolaminen und deren Quartärsalzen unter besonderer Berücksichtigung des Bronchospasmolytikums (-)-N-Ethylnorscopolamin-methobromid (Ba 253 BR).

The synthesis of anticholinergic N-alkylnorscopolamines and their quaternary salts, especially the synthesis of (-)-N-ethylnorscopolamin methobromide (Ba 253 BR), is reported. (-)-N-Ethylnorscopolamine methobromide differs from the stereoisomeric (-)-N-ethylscopolammonium bromide not only by its physico-chemical, but also by its pharmacological properties. (-)-N-Ethylnorscopolamine methobromide represents an anticholinergic bronchodilator with long duration of action.

[Biochemical studies with oxitropium bromide. 1. Pharmacokinetics and metabolism in the rat and dog]. / Biochemische Untersuchungen mit Oxitropiumbromid. 1. Pharmakokinetik und Metabolismus in Ratte und Hund.

The bronchospasmolytic drug (8r)-6 beta, 7 beta-epoxy-8-ethyl-3 alpha-[(-)-tropoyloxy]-1 alpha H, 5 alpha H-tropanium bromide (oxitropium bromide, Ba 253 BR, Ventilat) was tested pharmacokinetically as a 14C labelled substance in rats and dogs. Following oral administration low concentrations of radioactivity persisting over several hours were measured in the blood of dogs and rats. The active ingredient which can be separated from the metabolites by thin layer chromatography and quantified via the radioactivity reaches a maximum in the rat plasma after 1 to 2 h; it is then eliminated from the blood with a half-life of approx. 4 h. Following intravenous administration the radioactivity measured directly (active ingredient + metabolites) is distributed rapidly into the tissue of the rat and the dog. The distribution phase is followed by a relatively fast elimination phase ending in the terminal elimination phase approx. 1 h after administration. Rats and dogs eliminate the radioactivity mainly with the feces after oral administration, whereas following intravenous administration the rat eliminates about half with the feces and half via the kidneys. Biliary excretion of the rat is 12% after oral and 14% after intravenous administration. The rat absorbs 14% and the dog 28% of dose. Five metabolites have been demonstrated in the urine of the rat and the dog. Metabolism takes place exclusively in the tropaic acid part of the molecule and by hydrolysis of the compound.

Carbon-13-N.M.R.-spectra of antamanide, several analogues and their alkali ion complexes.

Natural abundance carbon-13 Fourier transform n.m.r.-spectra were obtained of the cyclic decapeptides [Phe4Val6] antamanide (I); antamanide (II); [Tyr5] antamanide (III); [Ala1] antamanide (IV) and their ion complexes (I)-Na+, (II)-Na+, (II)-Li+, (III)-Na+ and (IV)-Na+. Based upon literature data, systematic comparisons and model compounds, a line assignment approach was performed for the majority of the aliphatic carbons. The spectra of the [Ala9Val6] analogues (V) (Bystrov et al., 1972) and II (measured in CD3CN Patel, 1973a, b) and their complexes were also assigned. Characteristic chemical shift variations observed upon complex formation were calculated (delta delta free peptide[Me+ complex) for a number of corresponding carbons, revealing shift changes up to 2.4 p.p.m. Preliminary calculations of the theta angle at selected prolines for some ion complexes are included.

Mass spectral analysis of glucuronides from sympathomimetic hydroxyphenylalkylaminoethanols.

A mass spectral method is described for the structure determination of glucuronic acid conjugates of hydroxyphenylalkylaminoethanol-type drugs. Trimethylsilylation and application of the GLC-mass spectral technique yield mass spectra with sufficient information for the identification of all structural subunits.

[A new method for technical synthesis of tertiary and quaternary d,1-tropic acid esters of some N-subsituted nortropan- and granatan-3-oles (author's transl)]. / Eine neue Methode zur technischen Darstellung von tertiären und quartären d,1-Tropasäureestern einiger N-substituierter Nortropan- bzw. Granatan-3-ole

A new technically feasible method for synthesizing atropine is described. This method can also be applied to N-substituted nortropan- and granatan-3-oles. The quaternization of these basic tropic acid ester yields new substances which have a pharmacological profile different from that of atropine. The stereoselectivity of the quanternization reaction is discussed.

[Studies on the pharmacokinetics and biotransformation of ipratropium bromide in the rat and dog]. / Untersuchungen zur Pharmakokinetik und Biotransformation von Ipratropiumbromid bei Ratte und Hund

The pharmacokinetics of the bronchodilator (8r)-3alpha-hydroxy-8-isopropyl-1alphaH,5alphaH-tropanium-bromide-(+/-)-tropate (ipratropiumbromide, Sch 1000, Atrovent) were studied in the rat and the dog after administering radioactive material (14C). The blood level of Sch 1000 following oral dosing showed plateaus in both the rat and the dog over a period of 2--8 h following administration. Subsequent elimination from the blood occurs with a half-life of 7h (rat) and 10 (dog). The half-life of elimination following i.v. administration is 1.9 h (rat) and 3.4 h (dog). In the rat biliary excretion occurs to the extent of 3.2% following oral dosing and 17.7% following i.v. application. In the same species renal excretion is 5.5% following oral administration and 58% following i.v. administration. Renal excretion in the dog, on the other hand, averaged 28% following oral and 55% following i.v. dosing, respectively. On the basis of a comparison of the areas under the blood level curves and also from the renal excretion following oral and i.v. dosing, i.e. disregarding absorption by gastrointestinal tissue, absorption was calculated as being 12% in the rat and 38% in the dog. Absorption in the rat after 1--3 h was calculated at 17--35% including the gastrointestinal tissue. Four metabolites and the unchanged substance could be detected in the 8-h urine of the rat. In the urine of the dog, the percentage of unchanged substance fell from a maximum of 81% (after 1 h) to 20% (after 47 h) in terms of radioactivity in the urine.