title: A molecular receptor selective for zwitterionic alanine.
abstract: A molecular receptor has been synthesized joining an aza-crown ether with a chiral chromane which mimics the oxyanion hole of the enzymes. With this receptor an apolar host-guest complex with zwitterionic alanine has been achieved through the formation of up to seven H-bonds. This complex allows the extraction of aqueous alanine to a chloroform phase, while other natural amino acids are poorly extracted or are not extracted at all. Due to the chiral nature of the receptor, enantioselective extraction from the aqueous alanine solution to a chloroform phase takes place. X-Ray analysis combined with anisotropic effects, NOE and CD studies revealed the absolute configuration of both strong and weak complexes. Modelling studies also support the proposed structures. The presence of an oxyanion-hole motif in this structure was corroborated by X-ray diffraction studies.
authors.affiliation: Organic Chemistry Department, University of Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain.
authors.forename: Omayra H
authors.initials: OH
authors.lastname: Rubio
authors.affiliation: Organic Chemistry Department, University of Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain.
authors.forename: Rachid
authors.initials: R
authors.lastname: Taouil
authors.affiliation: Department of Organic Chemistry, Faculty of Chemical Sciences, University of Concepción, Edmundo Larenas 129, PO Box 160-C, Concepción, Chile. muno_iz@yahoo.es.
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Muñiz
authors.affiliation: Organic Chemistry Department, University of Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Monleón
authors.affiliation: Engineering Chemistry Department, University of Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain.
authors.forename: Luis
authors.identifier: http://orcid.org/0000-0002-3781-0803
authors.initials: L
authors.lastname: Simón
authors.affiliation: X-Ray Diffraction Service, University of Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain.
authors.forename: Francisca
authors.initials: F
authors.lastname: Sanz
authors.affiliation: Organic Chemistry Department, University of Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain.
authors.forename: Joaquín R
authors.initials: JR
authors.lastname: Morán
mesh_terms: D000409:Alanine / Q000737:chemistry / Q000302:isolation & purification*; D001372:Aza Compounds / Q000737:chemistry*; D002839:Chromans / Q000737:chemistry*; D043844:Crown Ethers / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism
chemical_list: D001372:Aza Compounds; D002839:Chromans; D043844:Crown Ethers; D000409:Alanine