Small-Ring Compounds. VII. Physical and Chemical Properties of Cyclopropyl, Cyclobutyl, Cyclopentyl and Cyclohexyl Derivatives

Enthalpic and entropic contributions to the basicity of cycloalkylamines

Large-ring cycloalkylamines are slightly less basic than other cycloalkylamines such as cyclohexylamine, even though all have tetrahedral carbons and are strain-free. To understand why, enthalpy and entropy for protonation of a series of cycloalkylamines were accurately determined by isothermal titration calorimetry in 3 : 1 methanol–water. The study required resolving a discrepancy between these measurements and those in pure water. The data show that the lower basicity of large-ring cycloalkylamines is not due to enthalpy but to a more negative entropy of protonation. Computations show that this can be attributed in part to an entropy of conformational mixing, but the dominant contribution is steric hindrance to solvation, also corroborated by computation.

Large-ring cycloalkylamines are slightly less basic than other cycloalkylamines such as cyclohexylamine, even though all have tetrahedral carbons and are strain-free.

Cyclopropyl-tryptamine analogues: synthesis and biological evaluation as 5-HT(6) receptor ligands

Conformational restrictions: Based on the pharmacophore model for 5-HT(6) receptor ligands (shown), tryptamine analogues bearing a cyclopropyl ring on the α-position of the tryptamine side chain were synthesized and evaluated against 5-HT receptors. N,N-Dimethyl-1-arylsulfonyltryptamine derivatives exhibited promising selectivity for 5-HT(6) over 5-HT(1a) and 5-HT(4) receptors and interesting activity against 5-HT(6) (K(i) =∼0.15 μM; IC(50) =∼0.20 μM).

Protonic and Temperature Modulation of Constituent Expression by Component Selection in a Dynamic Combinatorial Library of Imines

The constitutional recomposition of a dynamic library of imines displays a complex behavior under the effect of two parameters, acidity and temperature. A qualitative analysis of the quantitative data is presented. The results illustrate the response of such a dynamic system to a physical stimulus (temperature) and a chemical effector (H+), thus demonstrating its adaptive behavior under the pressure of external factors. They also point to the possibility of modulating a given functional property (optical, electronic, ionic) by constitutional recomposition induced by a specific trigger. Such features are of great interest for the development of stimuli-responsive, functional dynamic materials.

Synthesis and Characterization of New Symmetrical Binucleating Ligands and Their &mgr;-Phenoxo-Bridged Bicopper(II) Complexes: Structural, Electrochemical, and Magnetic Studies

The new pentadentate binucleating ligands 2,6-Bis[N-(3,5-dimethyl-2-hydroxybenzyl)-N-methylaminomethyl]-4-chlorophenol, H(3)L(1), and 2,6-bis[N-(3,5-dichloro-2-hydroxybenzyl)-N-cyclohexylaminomethyl]-4-methylphenol, H(3)L(2), and their binuclear copper(II) complexes of the general formulas [Cu(2)L(1)(X)] (X = OMe, OH, Br (1-3)) and [Cu(2)L(2)(X)] (X = OMe, OH, Br (4-6)) have been prepared. The molecular structure of the complex [Cu(2)L(1)(OMe)].MeOH was studied by X-ray crystallography. It exists as a discrete binuclear species in which the copper atoms are in a distorted square planar environment with two oxygen bridges provided by the phenolate of the ligand and methoxy exogenous donor and the Cu.Cu distance is 3.030 Å. A cyclic voltammetric study of the complexes shows two quasireversible reduction waves at negative potentials. A cryomagnetic investigation on powdered samples of the complexes (1-6) shows moderately strong antiferromagnetic coupling (-2J in the range 120-300 cm(-)(1)). A comparison of the electrochemical and magnetic properties of the complexes prepared from both ligands is discussed. Crystal data for the complex [Cu(2)L(1)(OMe)].MeOH: molecular formula C(30)H(39)ClCu(2)N(2)O(5), monoclinic, space group P2(1)/c with a = 13.222(1) Å, b = 15.912(1) Å, c = 14.149(1) Å, beta = 91.64(1) degrees, and Z = 4.

Muscarinic activity of some secondary and tertiary amines and quaternary ammonium salts structurally related to oxotremorine

A number of secondary and tertiary amines as well as quaternary ammonium compounds, obtained by structural modification of the amino group of oxotremorine (1) and its acetamide analogue (14), were investigated for muscarinic and antimuscarinic activity in vivo and in vitro. For the quaternary ammonium analogues, decrease of in vitro muscarinic potency is well correlated with increase of the size of the quaternary ammonium group, as estimated from increments in apparent molal volumes. A similar decrease of muscarinic potency with increasing substitution at the nitrogen atom is generally observed for the secondary and tertiary amines. For the latter the reduction in muscarinic activity appears to be due to loss of efficacy, since the higher homologues are partial agonists or antagonists. There is a highly significant correlation between muscarinic activity in vitro and central tremorogenic activity of the tertiary amines.