title: Synthesis and biological activity of a series of potent fluoromethyl ketone inhibitors of recombinant human calpain I.
abstract: 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 I (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 microM, respectively. Finally, we also disclose the first example of fluorination of a dipeptide enol silyl ether to generate the corresponding dipeptide fluoromethyl ketone.
authors.affiliation: Department of Chemistry, Cephalon, Inc., West Chester, Pennsylvania 19380-4245, USA.
authors.forename: S
authors.initials: S
authors.lastname: Chatterjee
authors.forename: M A
authors.initials: MA
authors.lastname: Ator
authors.forename: D
authors.initials: D
authors.lastname: Bozyczko-Coyne
authors.forename: K
authors.initials: K
authors.lastname: Josef
authors.forename: G
authors.initials: G
authors.lastname: Wells
authors.forename: R
authors.initials: R
authors.lastname: Tripathy
authors.forename: M
authors.initials: M
authors.lastname: Iqbal
authors.forename: R
authors.initials: R
authors.lastname: Bihovsky
authors.forename: S E
authors.initials: SE
authors.lastname: Senadhi
authors.forename: S
authors.initials: S
authors.lastname: Mallya
authors.forename: T M
authors.initials: TM
authors.lastname: O'Kane
authors.forename: B A
authors.initials: BA
authors.lastname: McKenna
authors.forename: R
authors.initials: R
authors.lastname: Siman
authors.forename: J P
authors.initials: JP
authors.lastname: Mallamo
mesh_terms: D002154:Calpain / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000378:metabolism; D056668:Cathepsin L; D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000378:metabolism; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology*; D004151:Dipeptides / Q000138:chemical synthesis / Q000494:pharmacology; D010450:Endopeptidases; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000138:chemical synthesis / Q000494:pharmacology; D007659:Ketones / Q000138:chemical synthesis* / Q000494:pharmacology*; D015458:Leukemia, T-Cell / Q000201:enzymology; D011994:Recombinant Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D006845:Hydrocarbons, Fluorinated; D007659:Ketones; D011994:Recombinant Proteins; D002403:Cathepsins; D010450:Endopeptidases; D002154:Calpain; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; C534281:CTSL protein, human; D056668:Cathepsin L