Breveglieri A, Guerrini R, Salvadori S, Bianchi C, Bryant S D, Attila M, Lazarus L H
Department of Pharmaceutical Sciences, University of Ferrara, Italy.
J Med Chem. 1996 Feb 2;39(3):773-80. doi: 10.1021/jm950490j.
Deltorphin analogues were substituted by a series of achiral C alpha,alpha-dialkyl cyclic alpha-amino acids (1-aminocycloalkane-1-carboxylic acids, Ac chi c, where chi = a hexane, pentane, or propane cycloalkane ring) in position 2, 3, 4, or 2 and 3 in deltorphin C, and in position 2 in [Ac6c2,-des-Phe3]deltorphin C hexapeptide. Receptor assays indicated that even though Ac6c2 and Ac6c3 exhibited a diminished Ki delta by ca. 20-fold (2.5-3.3 nM) relative to deltorphin C (Ki delta = 0.15 nM), selectivity was marginally elevated (Ki mu/Ki delta = 1250) or enhanced by about 70%, and both peptides fitted stringent iterative calculations for a two-site binding model (eta = 0.625 and 0.766, respectively, P < 0.0001). The disubstituted [Ac6c2,3]- or [Ac6c2,des-Phe3]deltorphin analogues yielded peptides with decreased Ki delta, such that the latter peptide was essentially inactive. The presence of Ac5c or Ac3c in place of Phe3 further diminished Ki delta (15.4 to 19.0 nM), yet delta selectivity only fell about one-half (Ki mu/Ki delta = 440 and 535, respectively), and only the former peptide fitted a two-site binding model (eta = 0.799). The replacement of Asp4 by Ac6c, Ac5c, or Ac3c produced essentially nonselective analogues through the acquisition of high mu affinities (2.5, 0.58 and 0.27 nM, respectively) while maintaining high delta affinities (Ki delta = 0.045-0.054 nM) which were about 3-fold greater than that of deltorphin C. Using pharmacological assays in vitro (mouse vas deferens and guinea pig ileum), position 3-substituted analogues all indicated substantial losses in bioactivity, whereas substitution by 1-aminocycloalkanes at the fourth position retained high delta activity. In fact, the bioactivity of [Ac3c4]deltorphin C indicated a peptide with relatively weak delta selectivity, which was comparable to the observations with the receptor binding data. In summary, the data confirmed that (i) delta selectivity occurs in the absence of D-chirality at position 2, (ii) the aromaticity of Phe3 is replaceable by an achiral residue with a hydrophobic ring-saturated side chain, and (iii) the acquisition of dual high-affinity analogues occurs through the elimination of the anionic function at position 4 and replacement by an amino acid with a hydrophobic side chain.
在德尔托啡肽C的第2、3、4位或第2和3位，以及在[Ac6c2,-去苯丙氨酸3]德尔托啡肽C六肽的第2位，用一系列非手性的α,α-二烷基环α-氨基酸（1-氨基环烷-1-羧酸，Ac χ c，其中χ = 己烷、戊烷或丙烷环烷环）取代德尔托啡肽类似物。受体分析表明，尽管Ac6c2和Ac6c3的Kiδ相对于德尔托啡肽C（Kiδ = 0.15 nM）降低了约20倍（2.5 - 3.3 nM），但选择性略有提高（Kiμ/Kiδ = 1250）或提高了约70%，并且两种肽都符合双位点结合模型的严格迭代计算（分别为η = 0.625和0.766，P < 0.0001）。双取代的[Ac6c2,3]-或[Ac6c2,去苯丙氨酸3]德尔托啡肽类似物产生的肽的Kiδ降低，使得后一种肽基本无活性。用Ac5c或Ac3c取代苯丙氨酸3进一步降低了Kiδ（15.4至19.0 nM），但δ选择性仅下降约一半（Kiμ/Kiδ分别为440和535），并且只有前一种肽符合双位点结合模型（η = 0.799）。用Ac6c、Ac5c或Ac3c取代天冬氨酸4通过获得高μ亲和力（分别为2.5、0.58和0.27 nM）产生了基本无选择性的类似物，同时保持了高δ亲和力（Kiδ = 0.045 - 0.054 nM），其比德尔托啡肽C大约高3倍。使用体外药理学分析（小鼠输精管和豚鼠回肠），第3位取代的类似物均表明生物活性大幅丧失，而在第4位用1-氨基环烷取代则保留了高δ活性。事实上，[Ac3c4]德尔托啡肽C的生物活性表明该肽的δ选择性相对较弱，这与受体结合数据的观察结果相当。总之，数据证实：（i）在第2位不存在D-手性时会出现δ选择性；（ii）苯丙氨酸3的芳香性可被具有疏水环饱和侧链的非手性残基取代；（iii）通过消除第4位的阴离子功能并用具有疏水侧链的氨基酸取代，可获得双高亲和力类似物。
