The properties of two inherently chiral cavitands in enantioselective recognition of N-methyl-leucine was studied in solution, through 1H and 31P NMR experiments, and in the solid state, through co-crystallisation experiments. The inherent chirality of the receptors was obtained through the desymmetrization of the rigid concave cavity by introducing three different bridging groups at the upper rim: two inward P=O groups, one inward P=S moiety and one methylene bridge in the AABC mode. For the solution studies, N-methyl-L-leucine was used as pure enantiomer and partial enantioselectivity was observed in the presence of an excess of a racemic mixture of cavitand receptor. Centrosymmetric crystals consisting of the complexes cR-cav1·N-methyl-D-leucine and cS-cav1·N-methyl-L-leucine were obtained from co-crystallisation of the racemic mixture of cR-cav/cS-cav 1 and N-methyl-D/L-leucine. Differently to the solution case, in the solid state the enantioselectivity of the chiral cavitand is complete and only the two enantiopure mirror complexes were obtained.

Inherently chiral phosphonate cavitands as enantioselective receptors for mono-methylated L-amino acids

Brancatelli, Giovanna;Geremia, Silvano;
2018-01-01

Abstract

The properties of two inherently chiral cavitands in enantioselective recognition of N-methyl-leucine was studied in solution, through 1H and 31P NMR experiments, and in the solid state, through co-crystallisation experiments. The inherent chirality of the receptors was obtained through the desymmetrization of the rigid concave cavity by introducing three different bridging groups at the upper rim: two inward P=O groups, one inward P=S moiety and one methylene bridge in the AABC mode. For the solution studies, N-methyl-L-leucine was used as pure enantiomer and partial enantioselectivity was observed in the presence of an excess of a racemic mixture of cavitand receptor. Centrosymmetric crystals consisting of the complexes cR-cav1·N-methyl-D-leucine and cS-cav1·N-methyl-L-leucine were obtained from co-crystallisation of the racemic mixture of cR-cav/cS-cav 1 and N-methyl-D/L-leucine. Differently to the solution case, in the solid state the enantioselectivity of the chiral cavitand is complete and only the two enantiopure mirror complexes were obtained.
22-dic-2017
Pubblicato
https://www.tandfonline.com/doi/full/10.1080/10610278.2017.1417991
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2917311
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