title: Peptides containing 4-amino-1,2-dithiolane-4-carboxylic acid (Adt): conformation of Boc-Adt-Adt-NHMe and NH...S interactions.
abstract: To study the conformational preferences induced by the insertion of the 4-amino-1,2-dithiolane-4-carboxylic acid (Adt) residue into a peptide backbone, the achiral N-protected dipeptide methylamide Boc-Adt-Adt-NHMe (1) was synthesized and its crystal state and solution conformation studied and compared with that exhibited by its carba-analogue Boc-Ac5c-Ac5c-NHMe containing two residues of 1-aminocyclopentane-1-carboxylic acid (Ac5c). Compound 1 in the crystal adopts a type-III beta-turn conformation and an analogous structure is that preferred in chloroform solution as established by 1H-NMR and NOE information. In the crystal packing three different Adt rings form a cavity and the involved sulphur atoms give rise to unusual multiple interactions with one NH group. The chemical nature of these intermolecular and intramolecular main-chain...side-chain NH...S interactions are discussed in terms of quantum chemical calculations.
authors.affiliation: Dipartimento di Studi Farmaceutici, Università di Roma La Sapienza and Istituto di Chimica Biomolecolare, Sezione di Roma, CNR, 00185 Roma, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Morera
authors.forename: Marianna
authors.initials: M
authors.lastname: Nalli
authors.forename: Adriano
authors.initials: A
authors.lastname: Mollica
authors.forename: Mario
authors.initials: M
authors.lastname: Paglialunga Paradisi
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Aschi
authors.forename: Enrico
authors.initials: E
authors.lastname: Gavuzzo
authors.forename: Fernando
authors.initials: F
authors.lastname: Mazza
authors.forename: Gino
authors.initials: G
authors.lastname: Lucente
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D003461:Crystallography; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D011789:Quantum Theory; D012996:Solutions; D013455:Sulfur / Q000737:chemistry; D013876:Thiophenes / Q000737:chemistry*
chemical_list: C416078:4-amino-1,2-dithiolane-4-carboxylic acid; D000596:Amino Acids; D009842:Oligopeptides; D012996:Solutions; D013876:Thiophenes; C501216:t-butoxycarbonyl-4-amino-1,2-dithiolane-4-carboxylic acid-4-amino-1,2-dithiolane-4-carboxylic acid methyl amide; D013455:Sulfur