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El grupo trifluorometilo como estabilizador conformacional y sonda: análisis conformacional de andamios de alcaloides
G K Surya Prakash1, Fang Wang, Martin Rahm
1Loker Hydrocarbon Research Institute, Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States.
Journal of the American Chemical Society
|July 1, 2014
Resumen
La adición de un grupo CF3 a la quinidina permite estudiar las conformaciones de alcaloides de cinchona utilizando RMN de flúor. Los modelos de solución empíricos predicen con precisión los efectos del disolvente, lo que ayuda a los estudios de reactividad.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Química Física es la química física.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los alcaloides de la cinchona son andamios conformacionalmente flexibles.
- Investigar el comportamiento conformacional es crucial para comprender sus propiedades y reactividad.
- La espectroscopia de resonancia magnética nuclear (19F NMR) con fluor-19 ofrece una sonda sensible para el análisis conformacional.
Objetivo del estudio:
- Para evaluar la precisión de los modelos de solvación teóricos (PCM) y empíricos (Kamlet-Taft) en la predicción de los efectos del disolvente en la conformación del alcaloide de la cinchona.
- Para investigar el comportamiento conformacional de la quinidina y la 9-epi-quinidina en varios disolventes.
- Para dilucidar el papel de los cambios conformacionales inducidos por el disolvente en la reactividad de los alcaloides de cinchona.
Principales métodos:
- Modificación de la quinidina con un grupo CF3 en la posición C9 para mejorar la estabilidad conformacional.
- Utilizando la espectroscopia de RMN 19F para determinar las distribuciones conformacionales en diferentes disolventes.
- Aplicación de métodos de relación de energía libre lineal (LFER) para evaluar modelos de solvación.
- Empleando ecuaciones de tipo Karplus para el análisis conformacional.
- Presentación de un modelo de reacción SN2 para estudiar la reactividad dependiente del disolvente.
Principales resultados:
- La introducción del grupo CF3 aumentó significativamente la barrera de interconversión conformacional del andamio alcaloide de la cinchona.
- Los modelos de solución empíricos (Kamlet-Taft) proporcionaron predicciones precisas de los efectos del disolvente en la conformación.
- El modelo teórico de solvación PCM mostró una fiabilidad relativamente baja en este estudio.
- El comportamiento conformal de la quinidina y la 9-epi-quinidina se investigó con éxito utilizando modelos empíricos y ecuaciones de Karplus.
Conclusiones:
- La RMN de flúor-19 es una herramienta poderosa para estudiar las conformaciones de alcaloides de cinchona, especialmente cuando se modifica con un grupo CF3.
- Los modelos de solvación empíricos son fiables para predecir los efectos del disolvente en estos sistemas.
- Los cambios conformacionales inducidos por solventes juegan un papel importante en la reactividad de los alcaloides de cinchona, como lo demuestra el modelo de reacción SN2.
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