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At least 829 records · Page 46Linked to original sources
PubMed1998

N-n-Propyl-substituted 3-(dimethylphenyl)piperidines display novel discriminative properties between dopamine receptor subtypes: synthesis and receptor binding studies.

3-Phenylpiperidines (PPEs) have been thoroughly investigated in view of their interesting dopaminergic activity, and the N-n-propyl substitution has been suggested as the most effective among several PPEs differently substituted on the phenyl ring. In previous studies, we found that the dimethyl substitution on the phenyl ring of N-unsubstituted PPEs provided compounds active toward alpha2-adrenergic receptors (alpha2-ARs), which proved to possess interesting selectivity properties. The high degree of homology between the binding domains of alpha2-ARs and D4-dopaminergic receptors (D4-DARs) prompted us to verify whether this kind of substitution on the aromatic ring might prove to be active against retinal DARs of the D4 subtype. On the basis of these premises, we synthesized the dimethylphenyl-substituted PPEs 4a-f, in which an n-propyl chain is present on the aminic nitrogen. Radioligand binding assays on bovine retina and striatum membranes for D1-like and D2-like DARs indicated that PPEs 4a, 4b, and 4f possess a high affinity and selectivity for the D4-DAR subtype of bovine retina.

Animals↗
PubMed2000

Stereo- and regiocontrolled construction of trisubstituted piperidines using a TpMo(CO)(2)(dihydropyridine) scaffold (Tp = hydridotrispyrazolylborate).

Cationic TpMo(CO)(2)(dihydropyridine) complexes (Tp = hydridotrispyrazolylborate), readily generated from 3-oxo-3, 6-dihydro-2H-pyridine-1-carboxylic acid benzyl ester, represent scaffolds from which (by judicious choice of demetalation conditions) either 2,3,6- or 2,5,6-trisubstituted-1,2,3, 6-tetrahydropyridines can be prepared in a regio- and stereodefined way.

Magnetic Resonance Spectroscopy↗
PubMed2001

Synthesis of DTPA analogues derived from piperidine and azepane: potential contrast enhancement agents for magnetic resonance imaging.

Two DTPA derivatives (PIP-DTPA and AZEP-DTPA) as potential contrast enhancement agents in MRI are synthesized. The T1 and T2 relaxivities of their corresponding Gd(III) complexes are reported. At clinically relevant field strengths, the relaxivities of the complexes are comparable to that of the contrast agent, Gd(DTPA) which is in clinical use. The serum stability of the (153)Gd-labeled complexes is assessed by measuring the release of (153)Gd from the ligands. The radiolabeled Gd chelates are found to be kinetically stable in human serum for up to at least 14 days without any measurable loss of radioactivity.

Contrast Media↗
PubMed2004

Electroreductive intramolecular coupling of aromatic beta- and gamma-imino esters: a new synthetic method for N-alkoxycarbonyl-2-aryl-3-ones and cis-2-aryl-3-ols of pyrrolidines and piperidines.

The electroreduction of aromatic beta- and gamma-imino esters prepared from beta-alanine and GABA in the presence of chlorotrimethylsilane and subsequent N-alkoxycarbonylation of the resulting five- and six-membered cyclized amines gave mixed ketals of N-alkoxycarbonyl-2-arylpyrrolidin-3-ones and 2-arylpiperidin-3-ones, respectively. The best result of the electroreductive intramolecular coupling was achieved using Bu(4)NClO(4) as a supporting electrolyte and a Pb cathode in THF. Acid hydrolysis of the mixed ketals afforded N-alkoxycarbonyl-2-arylpyrrolidin-3-ones and 2-arylpiperidin-3-ones in good yields. The reduction of these ketones with NaBH(4) in methanol afforded the corresponding N-alkoxycarbonyl-cis-2-arylpyrrolidin-3-ols and cis-2-arylpiperidin-3-ols diastereospecifically.

Amines↗
PubMed2000

Synthesis of enantiopure trans-3,4-disubstituted piperidines. An enantiodivergent synthesis of (+)- and (-)-paroxetine.

Reaction of (R)-phenylglycinol with methyl 5-oxopentanoate gave either bicyclic lactam cis-1 (the kinetic product) or its isomer trans-1 (under equilibrating conditions) as the major products, which were converted to the corresponding (cis or trans) unsaturated lactams 4 and 5. On treatment with lithium alkyl (or aryl) cyanocuprates, these chiral building blocks undergo conjugate addition to give enantiopure trans-3,4-substituted 2-piperidone derivatives in high yield and stereoselectivity. The synthetic potential of this transformation is illustrated by the synthesis of (+)-femoxetine and the two enantiomers of the known antidepressant paroxetine.

Antidepressive Agents, Second-Generation↗
PubMed2004

Tetradehydrohalicyclamine A and 22-hydroxyhalicyclamine A, new cytotoxic bis-piperidine alkaloids from a marine sponge Amphimedon sp.

Two new 3-alkylpiperidine alkaloids, tetradehydrohalicyclamine A (2) and 22-hydroxyhalicyclamine A (3), have been isolated from a marine sponge Amphimedon sp. as cytotoxic constituents. Their structures were elucidated by spectroscopic analysis. Compounds 2 and 3 inhibited growth of P388 cells with IC50 values of 2.2 and 0.45 microg/mL, respectively.

Alkaloids↗
PubMedDate not supplied

Alkaloids from dendrobatid frogs: structures of two omega-hydroxy congeners of 3-butyl-5-propylindolizidine and occurrence of 2,5-disubstituted pyrrolidines and a 2,6-disubstituted piperidine.

Forty alkaloids were detected and characterized from skin extracts of high- and low-elevation populations of the poison frog Dendrobates histrionicus from northwestern Colombia. Combined gc/ms with NH3 or ND3 in a chemical ionization mode detected protonated parent ions and determined the number of exchangeable NH and OH hydrogens. Six previously unknown dendrobatid alkaloids were characterized. Two were 2,5-disubstituted pyrrolidines, which included pyrrolidine 197B, a trans-2-butyl-5-pentylpyrrolidine, while a third was a 2,6-dipentylpiperidine. Indolizidines 239AB and 239CD had the same relative configuration as the parent alkaloid 223AB [(5E,9E)3-butyl-5-propylindolizidine] and contained, respectively, a omega-hydroxy group in the propyl or butyl side chain. The profiles of alkaloids in the new northern populations of D. histrionicus are typical of the species in containing a set of about eight histrionicotoxins, in marked contrast to a related species, Dendrobates lehmanni, which does not contain histrionicotoxins.

Alkaloids↗