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Efecto de la peracilación de la beta-ciclodextrina en la estructura molecular y en la formación de complejos de
M Añibarro1, K Gessler, I Usón
1Institut für Kristallographie, Freie Universität Berlin, Takustrasse 6, D-14195 Berlin, Germany.
Journal of the American Chemical Society
|November 29, 2001
Resumen
Las beta-ciclodextrinas peraciladas (CDs) exhiben estructuras distorsionadas y no planas debido al obstáculo estérico de la cadena acil. Este cierre de la cavidad intramolecular previene la formación de complejos de inclusión en solución.
Área de la Ciencia:
- Química supramolecular de las moléculas.
- Química de los carbohidratos Química de los carbohidratos
- La cristalografía es una técnica de cristalografía.
Sus antecedentes:
- Las beta-ciclodextrinas peraciladas (CDs) son ciclodextrinas modificadas con aplicaciones potenciales en la encapsulación molecular.
- Comprender su dinámica estructural y sus propiedades anfitrión-invitado es crucial para diseñar nuevos materiales funcionales.
Objetivo del estudio:
- Para dilucidar las estructuras moleculares de tres beta-ciclodextrinas peraciladas: heptakis(2,3,6-tri-O-acetil) -beta-CD (TA), heptakis(2,3,6-tri-O-propanoyl) -beta-CD (TP), y heptakis(2,3,6-tri-O-butanoyl) -beta-CD (TB). para el estudio de las estructuras moleculares de las tres beta-ciclodextrinas peraciladas: heptakis(2,3,6-tri-O-acetil) -beta-CD (TA), heptakis(2,3,6-tri-O-propanoyl) -beta-CD (TP), y heptakis(2,3,6-tri-O-butanoyl) -beta-CD (TB).
- Para investigar el comportamiento de inclusión en la fase de solución de estos CD peracilados con varias moléculas invitadas.
Principales métodos:
- El análisis de la estructura de rayos X de cristal único se empleó para determinar las estructuras tridimensionales precisas de TA, TP y TB.
- Se utilizó la espectroscopia de dicroísmo circular (CD) para estudiar la formación del complejo de inclusión en solución.
Principales resultados:
- La peracilación interrumpe el enlace de hidrógeno intramolecular, lo que lleva a la distorsión elíptica y estructuras no planas en forma de bote en los macrociclos.
- Las unidades de glucosa adoptan diferentes conformaciones ((4) C ((1)-silla o (O) S ((2)-skew-barco) para aliviar la tensión estérica de las cadenas de acilo.
- Se observó la autoinclusión intramolecular de cadenas acilo en la cavidad del CD, bloqueando efectivamente la cavidad.
- No se formaron complejos de inclusión en la solución, atribuidos al bloqueo de la cavidad inducido por la cadena acil.
Conclusiones:
- El estudio revela alteraciones estructurales significativas en las beta-ciclodextrinas peraciladas en comparación con los CD nativos.
- La inclusión de la cadena acil intramolecular es un factor clave que limita las capacidades huésped-invitado de estas ciclodextrinas modificadas en solución.
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