RESUMO
A catalytic hydrogenation of cannabidiol derivatives known as phenylcyclohexenes was used to prepare epimeric (1R,1S) and/or rotameric (M,P) phenylcyclohexanes. The reaction is diastereoselective, in favor of the 1S epimer, when large groups are attached to the phenyl ring. For each epimer, variable-temperature NMR experiments, including EXSY spectroscopy and DFT calculations, were used to determine the activation energies of the conformational exchange arising from the restricted rotation about the aryl-C(sp(3)) bond that led to two unequally populated rotamers. The conformational preference arises essentially from steric interactions between substituents vicinal to the pivot bond. The conformers of epimers (1S)-2e,f show high rotational barriers of up to 92 kJ mol(-1), unlike those of (1R)-2e,f and with much lower barriers of â¼72 kJ mol(-1). The height of the barriers not only depends on the substituents at the axis of chirality but also is influenced by the position of a methyl group on the monoterpene ring. The feature most favorable to high rotational barriers is when the methyl at C1 lies equatorially. This additional substituent effect, highlighted for the first time, seems fundamental to allowing atropisomerism in hindered ortho-substituted phenylcyclohexanes.
RESUMO
An improved enantioselective total synthesis of (-)-linderol A has been achieved via a five-step reaction with a 21% overall yield, starting from phloroacetophenone and (-)-alpha-phellandrene, two commercially available reagents. In the diastereoselective epoxidation step, the analysis of the two endocyclic epoxide intermediates reveals a hindered sp(2)-sp(3) rotation, which results in rotational diastereoisomers.
Assuntos
Benzofuranos/química , Benzofuranos/síntese química , Rotação , Cromatografia em Camada Fina , Compostos de Epóxi/química , Espectroscopia de Ressonância Magnética , Estereoisomerismo , Especificidade por SubstratoRESUMO
Structural analogues of Ilomastat (Galardin), containing unsaturation(s) and chain extension carrying bulky phenyl group or alkyl moieties at P'1 were synthesized and purified by centrifugal partition chromatography. They were analyzed for their inhibitory capacity towards MMP-1, MMP-2, MMP-3, MMP-9 and MMP-14, main endopeptidases involved in tumour progression. Presence of unsaturation(s) decreased the inhibitory potency of compounds but, in turn increased their selectivity for gelatinases. 2b and 2d derivatives with a phenyl group inhibited preferentially MMP-9 with IC50 equal to 45 and 38 nM, respectively, but also display activity against MMP-2 (IC50 equal to 280 and 120 nM, respectively). Molecular docking computations confirmed affinity of these substances for both gelatinases. With aims to obtain a specific gelatinase A (MMP-2) inhibitor, P'1 of Ilomastat was modified to carry one unsaturation coupled to an alkyl chain with pentylidene group. Docking studies indicated that MMP-2, but not MMP-9, could accommodate such substitution; indeed 2a proved to inhibit MMP-2 (IC50=123 nM), while displaying no inhibitory capacity towards MMP-9.
Assuntos
Indóis/química , Indóis/farmacologia , Inibidores de Metaloproteinases de Matriz , Modelos Moleculares , Inibidores de Proteases/química , Inibidores de Proteases/farmacologia , Alquilação , Dicroísmo Circular , Simulação por Computador , Ligação de Hidrogênio , Ácidos Hidroxâmicos/química , Ácidos Hidroxâmicos/farmacologia , Indóis/síntese química , Indóis/isolamento & purificação , Metaloproteinase 2 da Matriz/química , Metaloproteinase 2 da Matriz/metabolismo , Metaloproteinase 9 da Matriz/química , Metaloproteinase 9 da Matriz/metabolismo , Estrutura Molecular , Inibidores de Proteases/síntese química , Inibidores de Proteases/isolamento & purificação , Ligação Proteica , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
Some ilomastat analogues featuring an isobutylidene group or a 2-substituted indole nucleus were synthesized to evaluate their inhibitory activities against gelatinase A and stromelysin-1. Potent MMP-2 inhibition and good selectivity for that enzyme have been observed for compounds 1a, 2 and 22.