Porous Biomaterials via Side Chain‐Side Chain Interactions of Tyrosine Analogue of Pyridine Carboxamides

Abstract

AbstractPeptide based porous materials have attracted recent attention due to their environmentally benign nature. In an attempt to artificially imitate their importance, we have synthesized a set of three pseudopeptides comprising of a single pyridinedicarboxylic acid and a flexible dipeptidyl fragment H‐Xaa‐Yaa‐OMe (Xaa: L‐Ala, Yaa: mABA, pseudopeptide I ; Xaa: L‐Tyr, Yaa : mABA, pseudopeptide II; Xaa: L‐Ile, Yaa : Tyr, pseudopeptide III, mABA: meta amino benzoic acid ) using Boc chemistry. Our experimental analysis using X‐ray crystallography illustrates that pseudopeptide I–III displays supramolecular preference for double helices, characterestic of pyridine carboxamides, employing intermolecular H‐bonding and π‐π analogy. To date, literature documentation reveals that the reported double helical motifs have been modulated either by utilizing DNA conjugates or rigid templates, mainly governed by the concept of backbone‐backbone interaction. However, to the best of our knowledge these novel examples represent one of the very few reports of the architectural design solely nucleated by ecofriendly amino acids driven by sidechain ‐ sidechain correspondence, exhibiting significant difference in self‐assembling properties. Our UV/Visible, concentration dependant NMR experiment and Circular Dichroism measurement complies with the solid state conformational analysis. Interestingly, the double helical ensemble of pseudopeptide II (Tyr analogue bearing additional H‐bonding ability of phenolic OH) unveil fifteen times more N2 sorption (65 cc/g) than pseudopeptide I (Ala, devoid of additional H‐bonding ability) (4.5 cc/g), furthermore emphasizing the dominant role of side chain ‐ side chain interaction in porous biomaterial design. Besides our findings also spotlights the relevance of positional displacement of Tyr‐mABA fragment in controlling gas adsorption properties (pseudopeptide III; 5 cc/g). Our morphological analysis using FE‐SEM inaddition supports our experimental observation.