N-terminal-blocked and N-terminal-free pseudo tripeptide Gly-Gly and Gly-Pro derivatives of 5-aminolevulinic acid (ALA) esters were synthesized as potential specific substrates for cellular peptidases and precursors for the production of the photosensitizer protoporphyrin IX (PpIX). These precursors were evaluated using human cell lines of either carcinoma or endothelial origin. N-blocked or N-free dipeptides-ALA-ethyl esters, but not tripeptides-ALA-ethyl esters (or dipeptides-ALA-ethyleneglycols,) were substrates for cellular peptidases and were metabolized to ALA. The precursors were hydrolyzed intracellularly involving serine-proteases and metalloproteases. Cell selectivity for human endothelial or carcinoma cells was observed for some of these dipeptides-ALA. Thus drugs coupled to Gly-Gly-/Gly-Pro-derivatives may selectively target defined cells in human cancer, depending on specific cellular activating pathways expressed by the cells. (C) 2003 Elsevier Science Ltd. All rights reserved.
A new class of α-ketoamide derivatives with potent anticancer and anti-SARS-CoV-2 activities
cap moiety, P1, P2 and P3 side chain positions were explored. Many derivatives displayed highly potent biological activities in proteasome inhibition and anticancer activity against a panel of six cancer cell lines, which were further rationalized by molecular modeling analyses. Furthermore, a representative α-ketoamide derivative was tested and found to be active in inhibiting the cellular infection