Synthesis of peptide derivatives of aspirin and their antibiogram

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Peptide derivatives of Aspirin (1 to 8) were synthesized by using Ac2O/AcOH reaction with Salicyclic acid. Aspirin was coupled with amino acid amide and dipeptide amide and tripeptide amide using its p-nitrophenyl (NP) ester. The ester (Aspirin–ONP) was prepared using p-nitro phenol and DCC in EtOAc and was precipitated using EtOH. The synthesis of dipeptide amides were carried out in solution by stepwise elongationof the peptide chain from the C-terminal amino acid by coupling one amino acid at a time using DCC/HOBt method. Boc-group was used for Nα protection of all amino acids. The Boc-group cleavage was carried outusing 50% TFA/CH2Cl2. The amidation of C-terminal amino acid was carried out by treating the corresponding Boc–amino acid–ONp esters with dry NH3 in presence of DCC and HOBt. These compounds were subjected to antibiotic susceptibility studies against the Pseudomonas fluorescens, Escherichia coli and Staphylococcus aureus. Methionine amide of aspirin was active on S. aureus. Glycyl-glycyl-phenylalanyl-leucine amide ofaspirin was moderately active on all the three bacterial strains used. Glycyl-Phenylalanyl-leucine amide of aspirin and glycyl-glycyl-methionine amide of aspirin were active on P. fluorescens. Leucine amides of aspirinwas moderately active on S. aureus Methionine amides of aspirin was highly active on E. coli. Phenylalanylleucine amides of aspirin and glycyl-glycyl-phenylalanyl-methionine amide of aspirin were active on none ofthe organisms used in this study. In general the peptide derivatives of aspirin (1,3,4,5,6,7) were not active on all the three microbes used. Compounds 2 and 8 were sensitive to none of the organisms used in this study. By the major study, we observed that the derivative of aspirin showed a greater influence in inhibiting the test organisms used.Keywords: Aspirin–ONp, Boc–N3 (t-butyl azido formate), HOBt (1-Hydroxy benzotriazole), DCC (N, N1–Dicyclo hexyl carbodiimide) and DCU (N, N1–Dicyclohexyl urea).