RESUMEN
Reactions that were once the exclusive province of synthetic catalysts can increasingly be addressed using biocatalysis. Through discovery of unnatural enzyme reactions, biochemists have significantly expanded the reach of enzymatic catalysis to include carbene transfer chemistries including olefin cyclopropanation. Here we describe hemoprotein cyclopropanation catalysts derived from thermophilic bacterial globins that react with diazoacetone and an unactivated olefin substrate to furnish a cyclopropyl ketone, a previously unreported reaction for enzyme catalysts. We further demonstrate that the resulting cyclopropyl ketone can be converted to a key cyclopropanol intermediate that occurs en route to the anti-hepatitis C drug grazoprevir.
Asunto(s)
Proteínas Bacterianas/química , Ciclopropanos/síntesis química , Hemoproteínas/química , Propanoles/síntesis química , Alquenos/química , Amidas , Compuestos Azo/química , Proteínas Bacterianas/genética , Biocatálisis , Carbamatos , Ciclización , Evolución Molecular Dirigida , Hemoproteínas/genética , Estructura Molecular , Mutagénesis Sitio-Dirigida , Prueba de Estudio Conceptual , Quinoxalinas/química , Sulfonamidas , Verrucomicrobia/químicaRESUMEN
Extending the scope of biocatalysis to important non-natural reactions such as olefin cyclopropanation will open new opportunities for replacing multi-step chemical syntheses of pharmaceutical intermediates with efficient, clean, and highly selective enzyme-catalyzed processes. In this work, we engineered the truncated globin of Bacillus subtilis for the synthesis of a cyclopropane precursor to the antithrombotic agent ticagrelor. The engineered enzyme catalyzes the cyclopropanation of 3,4-difluorostyrene with ethyl diazoacetate on a preparative scale to give ethyl-(1R, 2R)-2-(3,4-difluorophenyl)-cyclopropanecarboxylate in 79% yield, with very high diastereoselectivity (>99% dr) and enantioselectivity (98% ee), enabling a single-step biocatalytic route to this pharmaceutical intermediate.