Phosphinic peptide matrix metalloproteinase-9 inhibitors by solid-phase synthesis using a building block approach

The solid-phase synthesis of an array of different pseudopeptides containin g a phosphinic glycine-leucine moiety (-G Psi/{P(O)OH-CH2}L-)([1]) is descr ibed. The resulting pseudopeptides were shown to act as matrix metalloprote inase-9 (MMP-9) inhibitors. Starting from available materials, the protecte d amino acid isosters benzyloxy-carbonyl aminomethylphosphinic acid (glycin e analogue) and ethyl alpha-isobutylacrylate (leucine analogue) were synthe sized and coupled with the bis(trimethylsilyl)phosphonite. Protective group interchange yielded a protected phosphinic dipeptide building block 1 read y for use in solid-phase peptide synthesis, Solid-phase peptide synthesis w as performed with 9-fluorenylmethyloxycarbonyl (Fmoc) chemistry on a polyet hylene glycol polyamide (PEGA) support and the coupling of 1 (1.5 equiv) wa s carried out with standard activation. The P-4-P-2 and P-2'-P-4' positions of the pseudopeptides were designed by analogy of the cleavage sequences o f different natural extracellular matrix protein substrates with a syntheti c peptide substrate of MMP-9. The crude peptides were obtained in high yiel d and purity as determined by RP-HPLC, and were characterized by electrospr ay mass spectrometry and amino acid analysis after purification. Enzyme kin etic investigations with MMP-9 of the purified peptide inhibitors showed Ki values in the range from mM to nM.