Bile Acids-Amino Acids Conjugates and Bile Acids Amino Derivatives as Organocatalysts for Direct Asymmetric Aldol Reactions in Aqueous Media

In this work, bile acids-amino acids, L-proline and L-phenylalanine, conjugates and bile acids amino derivatives were successfully synthesized, characterized and employed as organocatalysts for direct asymmetric aldol reactions in aqueous medium. Bile acids-amino acids conjugates exhibited high catalytic activity, with the L-proline-based organocatalyst showing the highest efficiency, achieving yields up to 99%, high diastereoselectivity for the anti product and moderate enantioselectivity. The L-phenylalanine-based one demonstrated good catalytic performance, achieving yields up to 99% and good diastereoselectivity for the syn product. The environmental sustainability of these catalytic systems lies in the use of bio-based surfactants-amino acids conjugates utilizing water as the reaction medium, without the addition of any cosolvent, while aligning with the modern ethics of environmentally friendly practices. These findings reveal the potential of natural bile acids scaffolds as versatile and eco-friendly conjugates to afford highly efficiency in sustainable organocatalysis for successfully achieving organic transformations in aqueous environments.