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Novel Helical Metallocryptand for Size-Selective Recognition of Amino Acid Derivatives with Aliphatic Side Chains
Firdausiah S.
Chemistry A European Journal
Q1Abstract
Abstract The novel tris(salen)‐type metallocryptand, LNi 3 , was designed and synthesized. Its crystallographic analysis revealed the presence as a helical enantiomeric pair, right‐handed ( P ) and left‐handed ( M ) forms, rather than the meso form, which was energetically supported by density functional theory (DFT) calculations. This LNi 3 host was capable of recognizing amino acid derivatives by several non‐covalent interactions, showing a selectivity to those bearing an aliphatic side chain. Its shape‐persistent nature of the cryptand facilitated the size‐based discrimination, which was clearly demonstrated by 1 H NMR spectroscopic titration studies. Recognition of some of the guests caused the emergence of CD signals, indicating the biased P / M helix inversion equilibrium of LNi 3 . Three aliphatic side‐chain guests, Val , Ile , and Leu , caused an M ‐favored shifting, while two π‐containing side‐chain guests, Arg and Trp , showed a preference to the P form. This metallocryptand, LNi 3 , overcomes the limitation in recognition of less polar amino acids having an alkyl side chain and provides future applications in molecular recognition, biochemical sensing, and enantiomeric sensing.