RESUMO
A Brønsted acid catalyzed tandem process to access densely functionalized chromeno[3,2-d]isoxazoles with good to excellent yields and diastereoselectivities was disclosed. The procedure is proposed to involve a 1,6-conjugate addition/electrophilic addition/double annulations process of alkynyl o-quinone methides (o-AQMs) in situ generated from o-hydroxyl propargylic alcohols with nitrones. Mild conditions, good functional group compatibility, easy scale-up of the reaction, and further product transformation demonstrated its potential application.
RESUMO
Aza-peptide Michael acceptors are a novel class of inhibitors that are potent and specific for caspases-2, -3, -6, -7, -8, -9, and -10. The second-order rate constants are in the order of 10(6) M(-1) s(-1). The aza-peptide Michael acceptor inhibitor 18t (Cbz-Asp-Glu-Val-AAsp-trans-CH=CH-CON(CH(2)-1-Naphth)(2) is the most potent compound and it inhibits caspase-3 with a k(2) value of 5620000 M(-1) s(-1). The inhibitor 18t is 13700, 190, 6.4, 594, 37500, and 173-fold more selective for caspase-3 over caspases-2, -6, -7, -8, -9, and -10, respectively. Aza-peptide Michael acceptors designed with caspase specific sequences are selective and do not show any cross reactivity with clan CA cysteine proteases such as papain, cathepsin B, and calpains. High-resolution crystal structures of caspase-3 and caspase-8 in complex with aza-peptide Michael acceptor inhibitors demonstrate the nucleophilic attack on C2 and provide insight into the selectivity and potency of the inhibitors with respect to the P1' moiety.
Assuntos
Compostos Aza/síntese química , Inibidores de Caspase , Oligopeptídeos/síntese química , Compostos Aza/química , Caspase 10 , Caspase 2 , Caspase 3 , Caspase 6 , Caspase 7 , Caspase 9 , Caspases/química , Cristalografia por Raios X , Cinética , Modelos Moleculares , Oligopeptídeos/química , Relação Estrutura-AtividadeRESUMO
Aza-peptide epoxides, a novel class of irreversible protease inhibitors, are specific for the clan CD cysteine proteases. Aza-peptide epoxides with an aza-Asp residue at P1 are excellent irreversible inhibitors of caspases-1, -3, -6, and -8 with second-order inhibition rates up to 1 910 000 M(-1) s(-1). In general, the order of reactivity of aza-peptide epoxides is S,S > R,R > trans > cis. Interestingly, some of the R,R epoxides while being less potent are actually more selective than the S,S epoxides. Our aza-peptide epoxides designed for caspases are stable, potent, and specific inhibitors, as they show little to no inhibition of other proteases such as the aspartyl proteases porcine pepsin, human cathepsin D, plasmepsin 2 from P. falciparum, HIV-1 protease, and the secreted aspartic proteinase 2 (SAP-2) from Candida albicans; the serine proteases granzyme B and alpha-chymotrypsin; and the cysteine proteases cathepsin B and papain (clan CA), and legumain (clan CD).
Assuntos
Compostos Aza/síntese química , Inibidores de Caspase , Compostos de Epóxi/síntese química , Oligopeptídeos/síntese química , Compostos Aza/química , Caspase 1/química , Caspase 3 , Caspase 6 , Caspase 8 , Caspases/química , Cristalografia por Raios X , Desenho de Fármacos , Estabilidade de Medicamentos , Compostos de Epóxi/química , Humanos , Hidrólise , Estrutura Molecular , Oligopeptídeos/química , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
Aza-peptide epoxides, a new class of irreversible protease inhibitors, are specific for the clan CD cysteine proteases. The inhibitors have second-order rate constants up to 10(5) M(-1) s(-1), with the most potent epoxides having the S,S stereochemistry. The aza-Asn derivatives are effective legumain inhibitors, while the aza-Asp epoxides were specific for caspases. The inhibitors have little or no inhibition with other proteases such as chymotrypsin, papain, or cathepsin B.
Assuntos
Compostos Aza/síntese química , Inibidores de Cisteína Proteinase/síntese química , Compostos de Epóxi/síntese química , Oligopeptídeos/síntese química , Compostos Aza/química , Inibidores de Caspase , Catepsina B/antagonistas & inibidores , Cristalografia por Raios X , Cisteína Endopeptidases , Inibidores de Cisteína Proteinase/química , Compostos de Epóxi/química , Cinética , Oligopeptídeos/química , Papaína/antagonistas & inibidores , Proteínas de Plantas/antagonistas & inibidores , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
Aza-peptide Michael acceptors are a new class of irreversible inhibitors that are highly potent and specific for clan CD cysteine proteases. The aza-Asp derivatives were specific for caspases, while aza-Asn derivatives were effective legumain inhibitors. Aza-Lys and aza-Orn derivatives were potent inhibitors of gingipain K and clostripain. Aza-peptide Michael acceptors showed no cross reactivity toward papain, cathepsin B, and calpain.
Assuntos
Compostos Aza/síntese química , Inibidores de Caspase , Inibidores de Cisteína Proteinase/síntese química , Peptídeos/síntese química , Adesinas Bacterianas , Compostos Aza/química , Caspases/química , Cisteína Endopeptidases/química , Inibidores de Cisteína Proteinase/química , Cisteína Endopeptidases Gingipaínas , Hemaglutininas/química , Cinética , Peptídeos/químicaRESUMO
A series of peptidyl alpha-ketoamides with the general structure Cbz-L-Leu-D,L-AA-CONH-R were synthesized and evaluated as inhibitors for the cysteine proteases calpain I, calpain II, and cathepsin B. Nucleobases, methylpiperazine, and dimethylaminoalkyl groups were incorporated into the primed region of the inhibitors to generate compounds that potentially cross the blood-brain barrier. Two of these compounds (Cbz-Leu-D,L-Abu-CONH-(CH(2))(3)-adenin-9-yl and Cbz-Leu-D,L-Abu-CONH-(CH(2))(3)-(4-methylpiperazin-1-yl) have been shown to have useful concentrations in the brain in animals. The best inhibitor for calpain I was Cbz-Leu-D,L-Abu-CONH-(CH(2))(3)-2-methoxyadenin-9-yl (K(i) = 23 nM), and the best inhibitor for calpain II was Cbz-Leu-D,L-Phe-CONH-(CH(2))(3)-adenin-9-yl (K(i) = 68 nM). On the basis of the crystal structure obtained with heterocyclic peptidyl alpha-ketoamides, we have improved inhibitor potency by introducing a small hydrophobic group on the adenine ring. These inhibitors have good potential to be used in the treatment of neurodegenerative diseases.
Assuntos
Adenina/análogos & derivados , Calpaína/antagonistas & inibidores , Dipeptídeos/síntese química , Piperazinas/síntese química , Adenina/síntese química , Adenina/química , Adenina/farmacocinética , Animais , Barreira Hematoencefálica/metabolismo , Calpaína/química , Catepsina B/antagonistas & inibidores , Catepsina B/química , Dipeptídeos/química , Dipeptídeos/farmacocinética , Feminino , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Estrutura Molecular , Piperazinas/química , Piperazinas/farmacocinética , Ligação Proteica , Relação Estrutura-Atividade , Suínos , Distribuição TecidualRESUMO
Caspase-3 is a prototypic executioner caspase that plays a central role in apoptosis. Aza-peptide epoxides are a novel class of irreversible inhibitors that are highly specific for clan CD cysteine proteases. The five crystal structures of caspase-3-aza-peptide epoxide inhibitor complexes reported here reveal the structural basis for the mechanism of inhibition and the specificities at the S1' and the S4 subsites. Unlike the clan CA cysteine proteases, the catalytic histidine in caspase-3 plays a critical role during protonation and subsequent ring opening of the epoxide moiety and facilitates the nucleophilic attack by the active site cysteine. The nucleophilic attack takes place on the C3 carbon atom of the epoxide and results in an irreversible alkylation of the active site cysteine residue. A favorable network of hydrogen bonds involving the oxyanion hole, catalytic histidine, and the atoms in the prime site of the inhibitor enhance the binding affinity and specificity of the aza-peptide epoxide inhibitors toward caspase-3. The studies also reveal that subtle movements of the N-terminal loop of the beta-subunit occur when the P4 Asp is replaced by a P4 Ile, whereas the N-terminal loop and the safety catch Asp179 are completely disordered when the P4 Asp is replaced by P4 Cbz group.