Flexible 1-[(2-aminoethoxy)alkyl]-3-ar(o)yl(thio)ureas as novel acetylcholinesterase inhibitors. Synthesis and biochemical evaluation.

A series of flexible 1-(2-aminoethoxy)-3-ar(o)yl(thio)ureas was synthesized and assessed for antiacetylcholinesterase activity. This series was designed in order to optimize the spacer length linking the two pharmacophoric moieties, i.e., the basic nitrogen and the ar(o)yl(thio)-urea unit, and to test compounds with greater conformational flexibility. Thus, the replacement of the previously described spacer, 4-piperidinylethyl, by a linear ethoxyethyl chain gave compounds of slightly comparable potency, providing that they were correctly substituted. The results show that this new flexible spacer is compatible with high inhibitory activities. The optimal chain length corresponds to five methylene groups, allowing an efficient interaction between the two pharmacophoric units and the two reported hypothetical enzyme hydrophobic binding sites. Moreover, the initially optimized benzyl group, attached to the basic nitrogen, was found to be advantageously replaced by a cyclohexyl group, showing that an aromatic residue does not represent a prerequisite for activity.

Novel [2-(4-piperidinyl)ethyl](thio)ureas: synthesis and antiacetylcholinesterase activity.

A series of 1-ar(o)yl-3-[2-(1-benzyl-4-piperidinyl)ethyl](thio)urea derivatives was synthesized and evaluated for antiacetylcholinesterase activity. Most aroyl(thio)urea derivatives showed potent inhibitory activity in the sub-micromolar range. A comparable potency was obtained with the aryl(thio)urea analogues by replacing the phenyl with a 2-pyridyl group. The substituted guanidine variations proved to be almost inactive whereas the nitroethylene analogues appeared to be quite efficient. These results were interpreted in terms of the preferential cis-trans conformation of the aroyl(thio)urea and 2-pyridyl(thio)urea moieties involving the existence of hydrogen bonding. In vivo experiments showed that compound 7m had maximal antiamnestic activity at 0.03 mg/kg with a therapeutic ratio greater than 1000, while cholinergic side effects were only seen at doses 100-fold the maximally effective antiamnestic dose. Compound 7m represents a potentially interesting antidementia agent.

New substituted 1-(2,3-dihydrobenzo[1, 4]dioxin-2-ylmethyl)piperidin-4-yl derivatives with alpha(2)-adrenoceptor antagonist activity.

The emergence of a novel theory concerning the role of noradrenaline in the progression and the treatment of neurodegenerative diseases such as Parkinson's and Alzheimer's diseases has provided a new impetus toward the discovery of novel compounds acting at alpha(2)-adrenoceptors. A series of substituted 1-(2, 3-dihydrobenzo[1,4]dioxin-2-ylmethyl)piperidin-4-yl derivatives bearing an amide, urea, or imidazolidinone moiety was studied. Some members of this series of compounds proved to be potent alpha(2)-adrenoceptor antagonists with good selectivity versus alpha(1)-adrenergic and D(2)-dopamine receptors. Particular emphasis is given to compound 33g which displays potent alpha(2)-adrenoceptor binding affinity in vitro and central effects in vivo following oral administration.