Skiles J W, Miao C, Sorcek R, Jacober S, Mui P W, Chow G, Weldon S M, Possanza G, Skoog M, Keirns J
Department of Medicinal Chemistry, Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Connecticut 06877.
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.
一系列在P1 - P1'位含有α,α - 二氟代甾酮残基且跨越S3 - S1'亚位点的三肽已被证明是人类白细胞弹性蛋白酶（HLE）的有效抑制剂。所描述的三肽在P2位含有非蛋白原性的无手性残基N - (2,3 - 二氢 - 1H - 茚 - 2 - 基)甘氨酸。先前已表明，在HLE的情况下，该残基是L - 脯氨酸的良好生物电子等排体替代物。在所制备的肽中，那些在P1 - 主要特异性位点含有L - 缬氨酸的α,α - 二氟亚甲基酮衍生物（二氟代甾酮）的肽是优选的残基。用L - 亮氨酸和L - 苯丙氨酸的相应α,α - 二氟亚甲基酮在P1位进行取代会得到无活性的化合物。在所描述的三肽中，体外活性最强的化合物是N - [N - CBZ - L - 缬氨酰 - N - (2,3 - 二氢 - 1H - 茚 - 2 - 基)甘氨酰] - 4(S) - 氨基 - 2,2 - 二氟 - 3 - 氧代 - 5 - 甲基己酸乙酯（17B）（IC50 = 0.635 microM）。据推测，抑制剂17b与HLE的S3 - S1'结合区域相互作用。此外，还制备了与HLE的S3 - S3'结合亚位点相互作用的延长结合抑制剂。为了实现与HLE的S1' - S3'亚位点的相互作用，利用了裂解肽的离去基团侧、基于甘氨酸 - 甘氨酸的间隔基团以及通过L - 赖氨酸的Nε连接的那些间隔基团。体外活性最强的延长化合物（P3 - P3'）之一是N6 - [4(S) - [[N - [N - CBZ - L - 缬氨酰 - N - (2,3 - 二氢 - 1H - 茚 - 2 - 基)甘氨酰]氨基] - 2,2 - 二氟 - 3 - 氧代 - 5 - 甲基己酰] - 2(S) - (乙酰氨基) - 6 - 氨基己酸甲酯（24b）（IC50 = 0.057 microM）。所描述的体外活性抑制剂也在仓鼠的弹性蛋白酶诱导的肺出血（EPH）模型中进行了评估。在该模型中，在HLE攻击（10微克，气管内给药）前5分钟气管内给药22c以剂量依赖性方式有效抑制出血（94.6%）。所描述的α,α - 二氟亚甲基酮抑制剂被认为作为过渡态类似物起作用。抑制过程可能通过与HLE的活性位点Ser195形成半缩酮而发生，并且α,α - 二氟亚甲基官能团的强吸电子效应促进了这一过程。
