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Relevant academic research and scientific papers

Synthesis and biological activity of a series of potent fluoromethyl ketone inhibitors of recombinant human calpain I

Calpain I, an intracellular cysteine protease, has been implicated in the neurodegeneration following an episode of stroke. In this paper, we report on a series of potent dipeptide fluoromethyl ketone inhibitors of recombinant human calpain I (rh calpain I). SAR studies revealed that while calpain I tolerates a variety of hydrophobic groups at the P1 site, Leu at P2 is preferred. However, the nature of the N-terminal capping group has a significant effect on the inhibitory activity of this series of compounds. Compound 4e [(1,2,3,4-tetrahydroisoquinolin-2-yl)carbonyl-Leu-D,L-Phe- CH2F], having a tetrahydroisoquinoline containing urea as the N-terminal capping group, is the most potent dipeptide fluoromethyl ketone inhibitor of calpain 1 (with a second-order rate constant for inactivation of 276 000 M- 1 s-1) yet reported; tripeptide 4k (Cbz-Leu-Leu-D,L-Phe-CH2F) is equipotent. A number of compounds presented in this study displayed excellent selectivity for calpain I over cathepsins B and L, two related cysteine proteases. Compounds which exhibited good inhibitory activity in the assay against isolated rh calpain I also inhibited intracellular calpain I in a human cell line. Thus, in an intact cell assay, compounds 4e and 4k inhibited calpain I with IC50 values of 0.2 and 0.1 μM, respectively. Finally, we also disclose the first example of fluorination of a dipeptide enol silyl ether to generate the corresponding dipeptide fluoromethyl ketone.

Potent fluoromethyl ketone inhibitors of recombinant human calpain I

We report on a series of potent and selective dipeptide fluoromethyl ketone inhibitors of recombinant human calpain I. Compound 4f, having a tetrahydroisoquinoline containing urea motif as N-terminus capping group, is the most potent member (k(obs)/I = 276,000 M-1 s-1) of this class. This compound was shown to prefer calpain I by >36-fold and approximately 4-fold over the related cysteine proteases, cathepsin B and cathepsin L, respectively.