Synthesis, characterization and antibacterial evaluation of novel substituted galactose thiazolidin-4-ones.
In this study, fifteen novel thiazolidinone derivatives were synthesized from galactose. In general it was observed that stereoselectivity for most of the 2R diastereomers was better than the 2S diastereomers. All compounds were characterized using NMR, melting point, optical rotation, FTIR, UV, HPLC, GC-MS and HRMS. In order to unequivocally assign each of the proton and carbon resonances, HMBC, HSQC, COSY and NOESY were used for both the 2-methoxy substituted diastereomers. The assignments in all the other compounds with electron donating groups were confirmed based on this. For the 2-nitro and 4-nitro derivatives, with electron withdrawing substituents, HMBC was used to confirm the assignments of the protons on the phenyl ring. Similarly, the protons on the aromatic ring were also confirmed by HMBC correlations for the 4-methoxy R diastereomer. Single crystal XRD was performed on the 2- methoxy R diastereomer, which confirmed the R configuration of one of the diastereomers in each of the pairs. This enabled us to differentiate between the R and S configuration at C-2 on the thiazolidinone ring. The synthesized compounds showed antibacterial activity against methicillin resistant Staphylococcus aureus, Klebsiella pneumonia, and Escherichia coli.