title: New 1H-pyrazole-containing polyamine receptors able to complex L-glutamate in water at physiological pH values.
abstract: The interaction of the pyrazole-containing macrocyclic receptors 3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.1(11,14)]-octacosa-1(27),11,14(28),24-tetraene 1[L1], 13,26-dibenzyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.1(1)(1,14)]-octacosa-1(27),11,14(28),24-tetraene 2[L2], 3,9,12,13,16,22,25,26-octaazatricyclo-[22.2.1.1(11,14)]-octacosa-1(27),11,14(28),24-tetraene 3[L3], 6,19-dibenzyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.1(11,)(14)]-octacosa-1(27),11,14(28),24-tetraene 4[L4], 6,19-diphenethyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.1(11,14)]-octacosa-1(27),11,14(28),24-tetraene 5[L5], and 6,19-dioctyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.1(11,14)]-octacosa-1(27),11,14(28),24-tetraene 6[L6] with l-glutamate in aqueous solution has been studied by potentiometric techniques. The synthesis of receptors 3-6[L3-L6] is described for the first time. The potentiometric results show that 4[L4] containing benzyl groups in the central nitrogens of the polyamine side chains is the receptor displaying the larger interaction at pH 7.4 (Keff = 2.04 x 10(4)). The presence of phenethyl 5[L5] or octyl groups 6[L6] instead of benzyl groups 4[L4] in the central nitrogens of the chains produces a drastic decrease in the stability [Keff = 3.51 x 10(2) (5), Keff = 3.64 x 10(2) (6)]. The studies show the relevance of the central polyaminic nitrogen in the interaction with glutamate. 1[L1] and 2[L2] with secondary nitrogens in this position present significantly larger interactions than 3[L3], which lacks an amino group in the center of the chains. The NMR and modeling studies suggest the important contribution of hydrogen bonding and pi-cation interaction to adduct formation.
authors.affiliation: Instituto de Química Médica, Centro de Química Orgánica Manuel Lora Tamayo, CSIC, C/ Juan de la Cierva 3, 28006 Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Miranda
authors.forename: Francisco
authors.initials: F
authors.lastname: Escartí
authors.forename: Laurent
authors.initials: L
authors.lastname: Lamarque
authors.forename: María J R
authors.initials: MJ
authors.lastname: Yunta
authors.forename: Pilar
authors.initials: P
authors.lastname: Navarro
authors.forename: Enrique
authors.initials: E
authors.lastname: García-España
authors.forename: M Luisa
authors.initials: ML
authors.lastname: Jimeno
mesh_terms: D040761:Biomimetic Materials / Q000138:chemical synthesis / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011073:Polyamines / Q000138:chemical synthesis / Q000737:chemistry*; D011199:Potentiometry; D011720:Pyrazoles / Q000138:chemical synthesis / Q000737:chemistry*; D017470:Receptors, Glutamate / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D011073:Polyamines; D011720:Pyrazoles; D017470:Receptors, Glutamate; D014867:Water; D018698:Glutamic Acid