title: Cyclopropane-derived peptidomimetics. Design, synthesis, and evaluation of novel enkephalin analogues.
abstract: It is known that peptide mimics containing trans-substituted cyclopropanes stabilize extended conformations of oligopeptides, and molecular modeling studies now suggest that the corresponding cis-cyclopropane dipeptide isosteres could stabilize a reverse turn. To begin to assess this possibility, a series of cis-substituted cyclopropanes were incorporated as replacements of the Gly(2)-Gly(3) and Phe(4)-Leu(5) dipeptide subunits in Leu-enkephalin (H(2)N-Tyr-Gly-Gly-Phe-Leu-OH), which is believed to bind to opiod receptors in a conformation containing a beta-turn. General methods for the synthesis of the cyclopropane-containing dipeptide isosteres -XaaPsi[COcpCO]Yaa- and -XaaPsi[NHcpNH]Yaa-were developed by a sequence that featured the enantioselective cyclization of allylic diazoacetates catalyzed by the chiral rhodium complexes Rh(2)[(5S)-MEPY](4) and Rh(2)[(5R)-MEPY](4). A useful modification of the Weinreb amidation procedure was applied to the opening of the intermediate lactones with dipeptides, and a novel method for the synthesis of substituted diaminocyclopropanes was also developed. The Leu-enkephalin analogues were tested in a panel of binding and functional assays, and although those derivatives containing cyclopropane replacements of the Gly(2)-Gly(3) exhibited low micromolar affinity for the mu-receptor, analogues containing such replacements for the Phe(4)-Leu(5) subunit did not bind with significant affinity to any of the opioid receptors. These results are discussed.
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas, Austin, Texas 78712, USA.
authors.forename: S F
authors.initials: SF
authors.lastname: Martin
authors.forename: M P
authors.initials: MP
authors.lastname: Dwyer
authors.forename: B
authors.initials: B
authors.lastname: Hartmann
authors.forename: K S
authors.initials: KS
authors.lastname: Knight
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003500:Cyclization; D003521:Cyclopropanes / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D015195:Drug Design; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D020128:Inhibitory Concentration 50; D008297:Male; D051379:Mice; D008968:Molecular Conformation; D018716:Molecular Mimicry; D011485:Protein Binding; D011957:Receptors, Opioid / Q000378:metabolism; D014649:Vas Deferens / Q000187:drug effects
chemical_list: D003521:Cyclopropanes; D011957:Receptors, Opioid; D004743:Enkephalin, Leucine