Spectroscopic and structural studies of allyl urethane derivative of Monensin A sodium salt

A new derivative of polyether antibiotic Monensin A sodium salt its allyl urethane (MON-UR2-Na) was synthesised and its structure was studied by X-ray, FT-IR, NMR, and ESI-MS methods. The results of these studies demonstrated that the oxygen atom of the CO urethane group is not engaged in the coordination of the Na+ as postulated previously. The crystal space group is P21 with a = 12.0378(11), b = 12.4495(11), c = 14.9690(14), β = 94.791(8) and Z = 2. The structure determined in the present study exhibits significant differences with respect to the earlier published structure of phenyl urethane of Monensin. A comparison of these structures clearly shows that not only the functional urethane group but also its substituent strongly influence the structure of this type of derivatives of Monensin A. X-ray data and spectroscopic and spectrometric behaviour of the new derivative of Monensin A are discussed in detail and compared to the structure of phenyl urethane of Monensin A sodium salt.