Synthesis and radioiodination of new dipeptide coupled with biologically active pyridine moiety

Abstract

New amino acid derivatives coupled with biologically active pyridine moiety were synthesized. The synthesized compounds were characterized by IR, mass, and 1H NMR spectra. All compounds had shown potent antibacterial activity against Escherichia coli which can be comparable to the standard drugs, Tetracyclin and Penicillin G sodium. A newly synthesized dipeptide derivative, ethyl 2-(3-(4-hydroxyphenyl)-2-(2-(pyridin-4-ylamino)acetamido)propanamido)-3-(1H-indol-3-yl)propanoate (EHPIP), was labeled with 125I by direct electrophilic substitution reaction with a high labeling yield of 90 ± 2.80 %, using chloramine-T as oxidizing agent. This study showed good in vitro and in vivo stability of the 125I-EHPIP. The biodistribution of the radiolabeled compound showed a lung uptake of 68.83 ± 0.23 % injected dose per gram tissue organ at 15 min post-injection in normal mice and retention in lungs remained high up to 30 min, while the clearance from the normal mice appeared to proceed via the renal system. Such a lung uptake is better than that of the recently discovered 99mTc(CO)5I and 99mTc-DHPM which have maximum lung uptake of 12.8 and 10.12 % injected dose/g tissue organ at 1 h and 2 min post-injection, respectively. As a conclusion, EHPIP is a newly synthesized dipeptide with a good antimicrobial activity, and the radioiodinated EHPIP could be used as a novel agent for lung perfusion scan.