Synthesis, crystal structure, DFT calculations and molecular docking of l-pyroglutamic acid

Abstract

In this work, l-pyroglutamic acid (abbreviated as LPGA) was synthesized via intramolecular condensation of l-glutamic acid. The slow evaporation technique is an appropriate method to obtain a good quality of LPGA single crystals. The UV–Vis, FT-IR and NMR spectra of LPGA were recorded. DFT calculations were performed using the B3LYP hybrid functional combined with the extended 6-311++G(d,p) basis set. All the intermolecular interactions within the LPGA crystal were examined via topological Atom-in-Molecules (AIM), and Hirshfeld surfaces (HS) analyses. Further, the non-covalent interactions (NCI) were studied on the basis of reduced density gradient (RDG) map. Electronic properties of LPGA, such as oscillator strength, HOMO-LUMO energy gap, and excitation energies were carried out applying the time dependent density functional theory (TD-DFT). The LPGA's vibrational modes and the assignment of its fundamental modes were performed based on the Total Energy Distribution (TED) calculations. The intramolecular stability of LPGA arising from charge delocalization and hyperconjugative interactions is investigated through natural bond orbital (NBO) analysis. The nonlinear optical (NLO) properties of the LPGA were evaluated via the first-order hyperpolarizability calculations. Finally, molecular docking analysis was carried out to identify the potency of inhibition of LPGA compound against acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and the beta-secretase 1 (BACE1) Alzheimer's enzymes.