Total Synthesis and Pharmacological Investigation of Cordyheptapeptide A.

The present investigation reports the synthesis of a phenylalanine-rich N -methylated cyclopeptide, cordyheptapeptide A ( 8 ), previously isolated from the insect pathogenic fungus Cordyceps sp. BCC 1788, accomplished through the coupling of N -methylated tetrapeptide and tripeptide fragments followed by cyclization of the linear heptapeptide unit. Structure elucidation of the newly synthesized cyclopolypeptide was performed by means of FT-IR, ¹H-NMR, 13 C-NMR, and fast atom bombardment mass spectrometry (FABMS), and screened for its antibacterial, antidermatophytic, and cytotoxic potential. According to the antimicrobial activity results, the newly synthesized N -Methylated cyclopeptide exhibited potent antibacterial activity against Gram-negative bacteria Pseudomonas aeruginosa and Klebsiella pneumoniae and antifungal activity against dermatophytes Trichophyton mentagrophytes and Microsporum audouinii at a concentration of 6 μg/mL, in comparison to the reference drugs, gatifloxacin and griseofulvin. In addition, cyclopolypeptide 8 displayed suitable levels of cytotoxicity against Dalton's lymphoma ascites (DLA) and Ehrlich's ascites carcinoma (EAC) cell lines.