Self-Assembly of Amphiphilic Dipeptide with Homo- and Heterochiral Centers and Their Application in Asymmetric Aldol Reaction
Sudipto Bhowmick, Li Zhang, Guanghui Ouyang, Minghua Liu
Chiral self-assembly has drawn increasing interest in supramolecular chemistry. Here, we have designed amphiphilic l-Pro–l-Glu and l-Pro–d-Glu dipeptides and investigated their chiral self-assembly as well as asymmetric catalytic performance to disclose the synergistic effect of two stereogenic centers in the self-assembly and catalysis. It was found that both of the diastereomeric dipeptides can easily self-assemble into organogels with nanofibers. When these nanofibers were used as a catalyst for the asymmetric aldol reactions, enhanced enantioselectivity was obtained compared with their molecular state. Moreover, the L–L isomer assemblies showed higher enantioselectivity than the L–D isomer. It was revealed that both the supramolecular chirality of the nanofiber and the chiral catalytic site of l-proline played important roles in the asymmetric catalysis. In addition, the synergistic effect of two homochiral centers led to more efficient supramolecular catalysis that the L–L assemblies showed high yields (up to 97%), anti-diastereoselectivity (up to 99%), and excellent enantioselectivity (up to >99%).
Circular dichroism, Stereochemistry, Cotton effect, Nanostructures, Materials, Biochemistry