Inhibition of human leukocyte elastase by N-substituted peptides containing alpha,alpha-difluorostatone residues at P1

J Med Chem. 1992 Dec 25;35(26):4795-808. doi: 10.1021/jm00104a004.


A series of tripeptides which contain alpha,alpha-difluorostatone residues at P1-P1' and span the S3-S1' subsites have been shown to be potent inhibitors of human leukocyte elastase (HLE). The tripeptides described contain the nonproteinogenic achiral residue N-(2,3-dihydro-1H-inden-2-yl)glycine at the P2-position. This redidue has previously been shown in the case of HLE to be a good bioisosteric replacement for L-proline. Of the peptides prepared, those which contain the alpha,alpha-difluoromethylene keton derivative of L-valine (difluorostatone) are the preferred residue at the P1-primary specificity position. Substitution at P1 by the corresponding alpha,alpha-difluoromethylene ketones of L-leucine and L-phenylalanine gives inactive compounds. Of the tripeptides described the most potent in vitro compound is ethyl N-[N-CBZ-L-valyl-N-(2,3-dihydro-1H-inden-2-yl)glycyl]- 4(S)-amino-2,2-difluoro-3-oxo-5-methylhexanoate (17B) (IC50 = 0.635 microM). It is presumed that the inhibitor 17b interacts with the S3-S1' binding regions of HLE. Additionally extended binding inhibitors were prepared which interact with the S3-S3' binding subsites of HLE. In order to effect interaction with the S1'-S3' subsites of HLE, the leaving group side of cleaved peptides, spacers based upon Gly-Gly, and those linked via the N epsilon of L-lysine were utilized. One of the most potent extended compounds (P3-P3') in vitro is methyl N6-[4(S)-[[N-[N-CBZ-L-valyl-N- (2,3-dihydro-1H-inden-2-yl)glycyl]amino]-2,2-difluoro-3-oxo-5- methylhexanoyl]-2(S)-(acetylamino)-6-aminohexanoate (24b) (IC50 = 0.057 microM). The described in vitro active inhibitors were also evaluated in hamsters in an elastase-induced pulmonary hemorrhage (EPH) model. In this model, intratracheal (it.) administration of 22c, 5 min prior to HLE challenge (10 micrograms, it.) effectively inhibited hemorrhage (94.6%) in a dose-dependent manner. The described alpha,alpha-difluoromethylene ketone inhibitors are assumed to act as transition-state analogs. The inhibition process presumably acts via hemiketal formation with the active site Ser195 of HLE, and is facilitated by the strongly electron withdrawing effect of the alpha,alpha-difluoromethylene functionality.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites / drug effects
  • Cricetinae
  • Humans
  • Hydrocarbons, Fluorinated / chemical synthesis*
  • Hydrocarbons, Fluorinated / chemistry
  • Hydrocarbons, Fluorinated / pharmacology
  • Leukocyte Elastase
  • Male
  • Mesocricetus
  • Models, Molecular
  • Molecular Sequence Data
  • Oligopeptides / chemical synthesis*
  • Oligopeptides / chemistry
  • Oligopeptides / pharmacology
  • Pancreatic Elastase / antagonists & inhibitors*
  • Structure-Activity Relationship
  • Turkeys


  • Hydrocarbons, Fluorinated
  • Oligopeptides
  • Pancreatic Elastase
  • Leukocyte Elastase