Spectroscopic studies, crystal structures and antimicrobial activities of a new lasalocid 1-naphthylmethyl ester

A new lasalocid 1-naphthylmethyl ester (NAFA) has been synthesised and studied by X-ray, 1H NMR, 13C NMR, FT-IR, UV-vis, fluorescence as well as by PM5 semiempirical methods. The crystals of NAFA belong to the monoclinic system with the space group P21 with a = 13.4251(5) Å, b = 17.1064(7) Å, c = 18.5454(7) Å, β = 98.924(4)° and Z = 4. Two conformers of NAFA have been observed for two symmetry-independent molecules in different crystal environments. The molecular conformation of NAFA is partially stabilized by three intramolecular hydrogen bonds, in which the keto group is not involved. The FT-IR spectrum of NAFA in chloroform indicates that in this solvent the equilibrium between two structures of NAFA is realized. In one of the structures, the keto group is hydrogen bonded while in the other one this group is not involved in any hydrogen bond. The two structures of NAFA are discussed in detail. The new ester which has been additionally tested for its antimicrobial properties shows a certain activity against Gram-positive bacteria, however no activity against Gram-negative bacteria and Candida.