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PubMed1990

[Intramolecular aromatic alkylation. 28. Synthesis and pharmacological testing of homologized and hydroxylated 3,4-dihydro-1'-methylspiro[naphthalin-1(2H),4'-piperidine].

The compounds 4, 8, and 10, prepared by standard methods, are converted to the phenylpyridylakanes 9; their methoiodides 11 are reduced to yield the tetrahydropyridines 12. Whereas the cyclisation of 12a gives the isomers 1f and 1g, 12b furnishes only the isomer 1i or 1k, respectively. H3PO4 is found to be more suitable than HBr to cyclize 12c and 12d to the homologues 1l and 1m. Treatment of 12c and 12d affords the bromides 13a and 13b by HBr-addition, which are isolated for the first time. Compounds 1l, 1b, 1c, and 1a exhibit a notable activity in the writhing test, whereas the hydroxylated derivatives 1h, 1e, and 1f are definitely less active. The homologue 1m is inactive.

Analgesics↗
PubMed1988

Piperidine ester derivatives in mass spectrometric analysis of fatty acids from human serum phospholipids and cholesteryl esters.

When fatty acids with unknown structural features are confronted in mass spectral analyses of complex mixtures the cleavage pattern from the widely used methyl ester derivatives is not always sufficiently informative. Their mass spectra often contain only weak signals for the parent or any other characteristic ions. Hence the advantages of piperidides were explored and compared with methyl esters in the structure elucidation of fatty acids from human serum phospholipids and cholesteryl esters. After separation with thin-layer chromatography the fractions were extracted and subjected to alkaline hydrolysis. Methyl esters were prepared using HCl-methanol. Piperidides were obtained by converting the fatty acids first to acyl chlorides via interaction with thionyl chloride and then to piperidyl carboxylates by action with 3-(hydroxymethyl)-N-methylpiperidine. The piperidide derivatives were found more suitable than the methyl esters for the structural analysis of fatty acids because the chain structure can be diagnostically examined according to the specific fragmentation induced by the radical cleavage.

Cholesterol Esters↗
PubMed1991

Conformational analysis. Part 16. Conformational free energies in substituted piperidines and piperidinium salts.

The conformational free energies (-delta G degree) of a number of 4-substituted piperdines and piperidinium salts have been determined by the J-value method. For the 4-substituted piperdines (R = Me, Phenyl, CO2Et, Br, OH, F) the relative conformer energies are almost identical to those of the analogous cyclohexanes. The methyl and phenyl compounds showed no change in the couplings on protonation, implying no change in the conformer energies. In contrast, in the remaining compounds with polar 4-substituents an almost constant stabilisation of the axial conformer of ca. 0.7 -0.8 kcal mol-1 was observed on protonation. In three cases (R = F, OH and Br) the conformational preference is reversed on protonation and the axial form is favored. The conformer energies of both the free bases and the piperidinium salts can be quantitatively predicted by molecular mechanics calculations using the COSMIC force-field, in which the electrostatic interactions are calculated by a simple Coulombic model with the partial atomic charges in the molecules given by the CHARGE2 routine, and an effective dielectric constant of five. The precise agreement obtained demonstrates conclusively that the electrostatic interactions between the substituents and the protonated nitrogen are the cause of the conformational changes on protonation, and that these can be modelled successfully using existing force-fields.

Magnetic Resonance Spectroscopy↗
PubMed1983

In vitro effect of the racemic mixture and the (-)enantiomer of N-n-propyl-3-(3-hydroxyphenyl)-piperidine (3-PPP) on postsynaptic dopamine receptors and on a presynaptic dopamine autoreceptor.

The racemic mixture and the (-)enantiomer of the putative dopamine autoreceptor agonist 3-PPP were investigated in vitro using dopamine-sensitive adenylate cyclase in homogenates of rat striatum as a model for a postsynaptic D1-receptor type and inhibition of electrically-evoked tritium overflow from rat striatal slices preincubated with [3H]choline and [3H]dopamine as a model for a postsynaptic D2- and a presynaptic dopamine autoreceptor type, respectively. In contrast, to apomorphine, neither the racemic mixture nor the (-)enantiomer exerted any effect, suggesting agonistic properties in all three receptor models. However, both (+/-)3-PPP and (-)3-PPP were weak antagonists at postsynaptic D1- and D2-receptors. The results of the present investigation suggest that the in vivo effects of 3-PPP are either the result of metabolic activation or that this drug activates an other dopamine autoreceptor type, pharmacologically different from that one modulating dopamine release.

Adenylyl Cyclases↗