Design and synthesis of novel sulfonamide-containing bradykinin hB(2) receptor antagonists. Synthesis and structure-relationships of α,α-tetrahydropyranylglycine.

A series of α,α-cycloalkylglycine sulfonamide compounds of general formula 1 has previously been identified by our group as selective human B(2)(hB(2)) receptor antagonists. Here we report the in vitro and in vivo BK antagonist activity of a further evolution of the series, consisting in compounds of the general formula 2, containing either an alkyl piperazine or a 4-alkyl piperidine ring bearing various positively charged groups (R'). These studies unexpectedly revealed quite a flat nanomolar/subnanomolar SAR for the binding affinity, while differences were seen in the in vitro functional activities. We propose that variations in the residence time may explain these results.

4-N-Hydroxy-4-[1-(sulfonyl)piperidin-4-yl]-butyramides as HDAC inhibitors.

A series of N-substituted 4-alkylpiperidine hydroxamic acids, corresponding to the basic structure of histone deacetylase (HDAC) inhibitors (zinc binding moiety-linker-capping group) has been previously reported by our group. Linker length and aromatic capping group connection were systematically varied to find the optimal geometric parameters. A new series of submicromolar inhibitors was thus identified, which showed antiproliferative activity on HCT-116 colon carcinoma cells. We report here the second part of the strategy used in our research group to find a new class of HDAC inhibitors, namely the SAR study for the compounds bearing a sulfonyl group on the piperidine nitrogen. In the present work, we have considered both sulfonamides and sulfonyl ureas.

Alkyl piperidine and piperazine hydroxamic acids as HDAC inhibitors.

We report here the strategy used in our research group to find a new class of histone deacetylase (HDAC) inhibitors. A series of N-substituted 4-alkylpiperazine and 4-alkylpiperidine hydroxamic acids, corresponding to the basic structure of HDAC inhibitors (zinc binding moiety-linker-capping group) has been designed, prepared, and tested for HDAC inhibition. Linker length and aromatic capping group connection were systematically varied to find the optimal geometric parameters. A new series of submicromolar inhibitors was thus identified, which showed antiproliferative activity on HCT-116 colon carcinoma cells.

hNK2 receptor antagonists. The use of intramolecular hydrogen bonding to increase solubility and membrane permeability.

Starting from in-house capped tripeptide libraries, we have developed two series of compounds as potent antagonists of the hNK(2) receptor with a reduced peptide character. These two series maintained a crucial amide bond, which could not be methylated or substituted with classical isostere without a dramatic loss in binding affinity, very likely due conformational changes. We report here the planning, synthesis and evaluation of molecules belonging to the selected chemical series, which contain a strategically placed hydrogen bond acceptor. The aim of the work was to improve membrane permeability via the formation of an intramolecular hydrogen bonding, and at the same time to maintain the structural characteristics geometry and polarity of the amide linkage so as to retain a relevant binding affinity for the biological target.

Structure-activity relationships of 6-methyl-benzo[b]thiophene-2-carboxylic acid (1-[(S)-1-benzyl-4-[4-(tetrahydropyran-4-ylmethyl)piperazin-1-yl]butylcarbamoyl]cyclopentyl)amide, potent antagonist of the neurokinin-2 receptor.

As part of a project aimed at the identification of a series of small, orally available antagonists for the hNK(2) receptor, starting from one of our capped dipeptide libraries, we succeeded in the chemical optimization of the first identified leads, finally producing a class of molecules with significant activity in our animal model after iv administration. We herein report the results of further chemical modifications made to reduce the overall peptide character of this series and the consequent improvement of their in vivo antagonist activity. The present work identified 6-methylbenzo[b]thiophene-2-carboxylic acid (1-[(S)-1-benzyl-4-[4-(tetrahydropyran-4-ylmethyl)piperazin-1-yl]butylcarbamoyl]cyclopentyl)amide (10i), endowed with subnanomolar potency in all the in vitro tests and being highly potent and of long duration upon in vivo testing after both iv and id dosing.

Cinnamic acids and mono-substituted benzoic acids as useful capping groups for the preparation of hNK2 receptor antagonists.

NK(2) antagonists have been reported to be potentially useful for the treatment of a number of chronic diseases, such as asthma, irritable bowel syndrome, cystitis, and depression. Starting from an in-house prepared library of capped dipeptides, we have identified a series of molecules with subnanomolar binding affinity for the hNK(2) receptor. These molecules are composed by three well-defined regions: a planar aromatic acyl system as N-terminal capping group, a rigid and quite lipophilic core, and a flexible and relatively hydrophilic C-terminal capping group. Here we report how we were able to manipulate the N-terminal capping group to obtain significant in vivo activity after i.v. and i.d. administration.

alpha,alpha-Cyclopentaneglycine dipeptides capped with biaryls as tachykinin NK(2) receptor antagonists.

The NK(2) receptor belongs to the family of tachykinin neurotransmitters. It has been reported to be involved in several pathological conditions, and selective antagonists are potentially useful drugs for the treatment of asthma, irritable bowel syndrome, cystitis, and depression. Starting from in-house capped dipeptide libraries, we were able to identify a number of molecules with sub-nanomolar binding affinity for the hNK(2) receptor. All were characterized by a rigid core structure with a strong constraint induced by an alpha,alpha-cyclopentaneglycine fragment. Herein we report the further elaboration of three initial basic structures. The planar benzothiophene group was substituted with a series of biphenyl and heterobiphenyl moieties that are well tolerated in terms of receptor affinity. The new compounds also maintained good antagonist potency in an in vitro functional assay, and a number of them showed significant in vivo activity after intravenous administration in our guinea pig model.

alpha,alpha-Cyclic aminoacids as useful scaffolds for the preparation of hNK(2) receptor antagonists.

MEN 15596 is a small molecule, potent and selective antagonist of NK(2) receptor, possessing high affinity and potency at the guinea-pig and human receptors whose pharmacological characterization has been recently published. Here we report how the corresponding class of compounds was derived from a tri-peptide library and the first optimization round to improve both in vitro activity and physicochemical properties.

Design and synthesis of novel sulfonamide-containing bradykinin hB2 receptor antagonists. 2. Synthesis and structure-activity relationships of alpha,alpha-cycloalkylglycine sulfonamides.

Recently we reported on the design and synthesis of a novel class of selective nonpeptide bradykinin (BK) B2 receptor antagonists (J. Med. Chem. 2006, 3602-3613). This work led to the discovery of MEN 15442, an antagonist with subnanomolar affinity for the human B2 receptor (hB2R), which also displayed significant and prolonged activity in vivo (for up to 210 min) against BK-induced bronchoconstriction in the guinea-pig at a dose of 300 nmol/kg (it), while demonstrating only a slight effect on BK-induced hypotension. Here we describe the further optimization of this series of compounds aimed at maximizing the effect on bronchoconstriction and minimizing the effect on hypotension, with a view to developing topically delivered drugs for airway diseases. The work led to the discovery of MEN 16132, a compound which, after intratracheal or aerosol administration, inhibited, in a dose-dependent manner, BK-induced bronchoconstricton in the airways, while showing minimal systemic activity. This compound was selected as a preclinical candidate for the topical treatment of airway diseases involving kinin B2 receptor stimulation.

Generation of a new class of hNK(2) receptor ligands using the 'fragment approach'.

The so called 'fragment approach' was applied in the search for new leads as selective hNK(2) antagonists. A first round of structural space exploration through the use of bond rigidity as scaffold to support the fragments, afforded 27a as 200 nM hNK(2) ligand. Further refinement gave MEN 14933 as a 16 nM hNK(2) ligand, selective versus hNK(1), of a novel class. Conformational analysis was used to study results and plan future work.