title: Guanidine-guanidinium cooperation in bifunctional artificial phosphodiesterases based on diphenylmethane spacers; gem-dialkyl effect on catalytic efficiency.
abstract: Diphenylmethane derivatives 1-3, decorated with two guanidine units, are effective catalysts of HPNP transesterification. Substitution of the methylene group of the parent diphenylmethane spacer with cyclohexylidene and adamantylidene moieties enhances catalytic efficency, with gem-dialkyl effect accelerations of 4.5 and 9.1, respectively. Activation parameters and DFT calculations of the rotational barriers around the C-Ar bonds indicate that a major contribution to the driving force for enhanced catalysis is entropic in nature.
authors.affiliation: Dipartimento di Chimica and IMC-CNR Sezione Meccanismi di Reazione, Università La Sapienza, P.le Aldo Moro 5, 00185 Roma, Italy. riccardo.salvio@uniroma1.it
authors.forename: Riccardo
authors.initials: R
authors.lastname: Salvio
authors.forename: Luigi
authors.initials: L
authors.lastname: Mandolini
authors.forename: Claudia
authors.initials: C
authors.lastname: Savelli
mesh_terms: D001559:Benzhydryl Compounds / Q000737:chemistry / Q000378:metabolism*; D055162:Biocatalysis; D019791:Guanidine / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001559:Benzhydryl Compounds; D009942:Organometallic Compounds; D010727:Phosphoric Diester Hydrolases; D019791:Guanidine; C010129:diphenylmethane