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Reacciones asimétricas directas de tipo anti-Mannich catalizadas por un aminoácido diseñado
Susumu Mitsumori1, Haile Zhang, Paul Ha-Yeon Cheong
1The Skaggs Institute for Chemical Biology and the Department of Chemistry, The Scripps Research Institute, La Jolla, California 92037, USA.
Journal of the American Chemical Society
|January 26, 2006
Resumen
Un nuevo catalizador, el ácido (3R,5R)-5-metil-3-pirrolidinecarboxílico (RR35), permite reacciones de tipo anti-Mannich altamente selectivas. Este organocatalizador logra un excelente estereocontrol y enantioselectividad en condiciones suaves con baja carga del catalizador.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis es la catálisis.
- Síntesis asimétrica de síntesis.
Sus antecedentes:
- La catálisis previa de (S) -prolina había producido productos syn-Mannich.
- Necesidad de catalizadores que produzcan productos anti-Mannich con alta selectividad.
- Desarrollo de organocatalizadores para reacciones directas asimétricas de Mannich.
Objetivo del estudio:
- Diseñar un nuevo catalizador para reacciones de tipo Mannich enantioselectivas y anti-selectivas.
- Investigar el rendimiento del catalizador en condiciones suaves y bajo carga.
- Validar predicciones computacionales a través de síntesis y pruebas experimentales.
Principales métodos:
- Diseño del ácido (3R,5R)-5-metil-3-pirrolidinecarboxílico (RR35) basado en los principios de la catálisis de la prolina.
- Estudios computacionales que utilizan el nivel teórico HF/6-31G* para predecir la efectividad del catalizador.
- Reacciones organocatalíticas experimentales tipo Mannich utilizando aldehídos no modificados y ésteres α-imino protegidos por N-PMP.
Principales resultados:
- El catalizador diseñado (RR35) fue sintetizado con éxito.
- Las reacciones produjeron productos anti-Mannich con alta diastereoselectividad (anti:syn 94:6 a 98:2).
- Se lograron excelentes enantioselectividades (>97% a >99% ee) bajo condiciones suaves y baja carga de catalizador (1-5 mol %).
Conclusiones:
- El nuevo catalizador RR35 promueve eficazmente las reacciones directas enantioselectivas anti-selectivas de tipo Mannich.
- Los resultados experimentales concuerdan cuantitativamente con las predicciones computacionales.
- El catalizador ofrece un método suave y eficiente para sintetizar valiosos productos anti-Mannich.
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