Design, synthesis and bioactivity evaluation of novel monomethyl auristatin F analogues.

Monomethyl auristatin F (MMAF), a synthetic analogue of the natural compound dolastatin 10, has garnered significant attention in cancer research due to its high potency in vitro. While previous studies have focused on modifying the N-terminal extension of the amino group and the C-terminal modification of the carboxyl group, there has been limited exploration into modifying the P1 and P5 side chains. In this study, we substituted the valine residue at the P1 position with various natural or unnatural amino acids and introduced triazole functional groups at the P5 side chain. Compounds 11k and 18d exhibited excellent inhibition on tubulin. Additionally, compound 18d demonstrated enhanced cytotoxicity against HCT116 cells compared to the parent compound MMAF, suggesting its potential as a cytotoxic payload for further antibody-drug conjugates (ADCs) development.