Opioid peptides: synthesis and biological properties of [(N<sup>γ</sup>-glucosyl,N<sup>γ</sup>-methoxy)-α,γ-diamino-(S)-butanoyl]<sup>4</sup>-deltorphin-1-neoglycopeptide and related analogues
作者:Fernando Filira、Barbara Biondi、Laura Biondi、Elisa Giannini、Marina Gobbo、Lucia Negri、Raniero Rocchi
DOI:10.1039/b306142f
日期:——
The [D-Ala2]deltorphin I sequence in which the aspartic acid residue is replaced by the Nγ-OCH3-α,γ-diamino (S) butanoyl residue was synthesized using the Fmoc-chemistry-based solid phase procedure. The resulting deltorphin analogue was chemoselectively glucosylated by reaction with unprotected D-glucose (Glc). The Asn4-, (2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-galactopyranosyl)-Asn4- and the (2-acetamido-2-deoxy-D-galactopyranosyl)-Asn4-deltorphin I were also prepared for comparison. The affinity of the new compounds for the δ-opioid receptor was expressed by the inhibition constant (Ki) of the binding of the δ-receptor selective ligand [3H]naltrindole (NTI) to rat brain membrane preparations. The in vitro biological activity of the synthetic peptides was compared with that of the μ-opioid receptor agonist dermorphin in guinea pig ileum (GPI) preparations and with that of the δ-opioid receptor agonist deltorphin I in mouse vas deferens (MVD) preparations. The substitution of Asp4 with Asn failed to affect drastically the Ki and IC50 values for δ-sites, suggesting that an electrostatic interaction does not play an essential role in the binding to δ-opioid sites. The steric hindrance of the side chain of the residue in position 4 affects binding to δ-sites. The increase of the Ki value is smaller when the sugar-peptide linkage involves the γ-nitrogen of the Dab residue in comparison with the Asn amide side chain.
利用基于 Fmoc 化学的固相程序合成了[D-Ala2]deltorphin I 序列,其中的天冬氨酸残基被 Nδ³-OCH3-δ±,δ³-二氨基 (S) 丁酰残基取代。通过与未受保护的 D-葡萄糖(Glc)反应,对得到的 deltorphin 类似物进行化学选择性葡萄糖基化。为了进行比较,还制备了 Asn4-、(2-乙酰氨基-3,4,6-O-三乙酰基-2-脱氧-δ²-D-吡喃半乳糖基)-Asn4- 和(2-乙酰氨基-2-脱氧-D-吡喃半乳糖基)-Asn4-德尔托啡 I。新化合物对δ-阿片受体的亲和力用δ-受体选择性配体[3H]纳曲吲哚(NTI)与大鼠脑膜制备物结合的抑制常数(Ki)来表示。在豚鼠回肠(GPI)制备物中,合成肽的体外生物活性与δ-阿片受体激动剂dermorphin的体外生物活性进行了比较;在小鼠输精管(MVD)制备物中,合成肽的体外生物活性与δ-阿片受体激动剂deltorphin I的体外生物活性进行了比较。将 Asp4 替换为 Asn 未能显著影响δ-位点的 Ki 值和 IC50 值,这表明静电相互作用在与δ-阿片位点的结合中并未发挥重要作用。第 4 位残基侧链的立体阻碍影响了与δ-位点的结合。当糖肽连接涉及 Dab 残基的δ-氮时,Ki 值的升高幅度比涉及 Asn 酰胺侧链时要小。