1. Symbols and abbreviations used in this paper follows the IUPAC−IUB Commission on Biochemical Nomenclature (J. Biol. Chem.1985,260, 1442). Boc,tert-butyloxycarbonyl; DAGO, [d-Ala2,N-Me-Phe4,Gly-ol5]enkephalin; deltorphin C, [d-Ala2]deltorphin I (H-Tyr-d-Ala-Phe-Asp-Val-Val-Gly-NH2); DMSO, dimethyl sulfoxide; Dmt, 2‘,6‘-dimethyl-l-tyrosine; DPDPE, [d-Pen2,5]enkephalin; Et2O, diethyl ether; EtOAc, ethyl acetate; GPI, guinea pig ileum; HOBt, 1-hydroxybenzotriazole; HPLC, high performance liquid chromatography;Ke, the antilog of pA2in molar concentration; Me, methyl group; MeOH, methanol; MVD, mouse vas deferens; pA2, the negative log of the molar concentration necessary to double the concentration of agonist needed to elicit the original response;tBu,tert-butyl; TEA, triethylamine; TFA, trifluoroacetic acid; Tic, 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid; TLC, thin-layer chromatography; WSC, 1-ethyl-3-(3‘-(dimethyl)aminopropyl)carbodiimide hydrochloride; Z, benzyloxycarbonyl.
2. The opioid peptides of the amphibian skin
3. The toad, ugly and venomous, wears yet a precious jewel in his skin
4. Opioid receptor selectivity reversal in deltorphin tetrapeptide analogues
5. The aspartic acid in deltorphin I and dermenkephalin promotes targeting to δ-opioid receptor independently of receptor binding