RESUMO
Ibudilast [1-(2-isopropylpyrazolo[1,5-a]pyridin-3-yl)-2-methylpropan-1-one] is a nonselective phosphodiesterase inhibitor used clinically to treat asthma. Efforts to selectively develop the PDE3- and PDE4-inhibitory activity of ibudilast led to replacement of the isopropyl ketone by a pyridazinone heterocycle. Structure-activity relationship exploration in the resulting 6-(pyrazolo[1,5-a]pyridin-3-yl)pyridazin-3(2H)-ones revealed that the pyridazinone lactam functionality is a critical determinant for PDE3-inhibitory activity, with the nitrogen preferably unsubstituted. PDE4 inhibition is strongly promoted by introduction of a hydrophobic substituent at the pyridazinone N(2) centre and a methoxy group at C-7' in the pyrazolopyridine. Migration of the pyridazinone ring connection from the pyrazolopyridine 3'-centre to C-4' strongly enhances PDE4 inhibition. These studies establish a basis for development of potent PDE4-selective and dual PDE3/4-selective inhibitors derived from ibudilast.
Assuntos
Inibidores de Fosfodiesterase/química , Pirazóis/química , Piridazinas/química , Piridinas/química , Teprotida , Sítios de Ligação , Ativação Enzimática/efeitos dos fármacos , Modelos Moleculares , Estrutura Molecular , Inibidores de Fosfodiesterase/farmacologia , Pirazóis/farmacologia , Piridazinas/farmacologia , Piridinas/farmacologia , Relação Estrutura-Atividade , Especificidade por Substrato , Teprotida/síntese química , Teprotida/química , Teprotida/farmacologiaRESUMO
Treatment of 5-(tert-butyldimethylsilyl)-2,3-O-isopropylidene-D-ribose with lithium acetylides gave mixtures of syn- and anti-alkynols 2a-2c which were separated following protection as methoxymethyl ethers. These were converted to the corresponding iodides which underwent 6-exo-dig radical cyclisation to afford chiral cyclohexanes and carbasugars. Oxidation of the primary alcohols 6a-b gave the corresponding aldehydes which on treatment with Grignard reagents afforded a mixture of alcohols. The corresponding iodides underwent similar 6-exo-dig cyclisation to give fully functionalised cyclohexanes.
RESUMO
Cycloaddition of pyridine N-imine with 6-alkyl-4-oxohex-5-ynoates followed by condensation with hydrazine provides concise access to pharmacologically active 6-(pyrazolo[1,5-a]pyridin-3-yl)pyridazinones. For the first time alkynyl heterocycles are also shown to be effective dipolarophiles for pyridine N-imine, and analogous compounds can be accessed directly in modest yields through the reaction of 6-(alkyn-1-yl)pyridazin-3-one derivatives.
Assuntos
Pirazóis/química , Pirazóis/síntese química , Piridinas/química , Piridinas/síntese química , Cristalografia por Raios X , Hidrazinas/química , Iminas/químicaRESUMO
A quantitative method has been developed for determining the affinity of substrates for the peptide transporter PepT1, allowing oral availability of drugs via PepT1 to be estimated.
Assuntos
Algoritmos , Peptídeos/química , Simportadores/química , Sítios de Ligação , Transporte Biológico , Estrutura Molecular , Transportador 1 de Peptídeos , Peptídeos/metabolismo , Especificidade por Substrato , Simportadores/metabolismoRESUMO
The stereochemistry of thiodipeptides of proline [e.g. Ala-Psi[CS-N]-Pro] can be controlled using pH, allowing the trans-preference for substrates of the peptide transporter PepT1 to be confirmed.
Assuntos
Proteínas de Membrana Transportadoras/química , Peptídeos/química , Compostos de Sulfidrila/química , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Proteínas de Membrana Transportadoras/metabolismo , Estrutura Molecular , Peptídeos/metabolismo , EstereoisomerismoRESUMO
The conformation at the first residue of dipeptide substrates for the peptide transporter PepT1 has been probed using constrained peptide analogues, and the active conformation has been identified.
Assuntos
Dipeptídeos/química , Simportadores/química , Modelos Moleculares , Transportador 1 de Peptídeos , Conformação Proteica , Especificidade por SubstratoRESUMO
Here, we show that recombinant bovine PDE5A1 is proteolysed by recombinant caspase-3 in in vitro and transfected Cos-7 cells. In addition, the treatment of PDE5A1-transfected Cos-7 and PC12 cells with staurosporine, an apoptotic agent that activates endogenous caspase-3, also induced proteolysis and inactivation of PDE5A1. These findings suggest that there is specificity in the interaction between caspase-3 and PDE5A1 that requires application of an apoptotic stimulus. The potential proteolysis of the [778]DQGD[781] site in PDE5A1 by caspase-3 might affect cGMP's hydrolyzing activity as this is within the boundary of the active site. We therefore created a truncated D781 mutant corresponding exactly to the potential cleavage product. This mutant was expressed equally well compared with the wild-type enzyme in transfected Cos-7 cells and was inactive. Inactivity of the truncated mutant was not due to potential misfolding of the enzyme as it eluted from gel filtration chromatography in the same fraction as the wild-type enzyme. Homology model comparison with the catalytic domain of PDE4B2 was used to probe a functional role for the region in PDE5A1 that might be cleaved by caspase-3. From this, we can predict that a caspase-3-mediated cleavage of the [778]DQGD[781] motif would result in removal of the C-terminal tail containing Q807 and F810, which are potentially important amino acids required for substrate binding.