title: Structural refinement of pyrazolo[4,3-d]pyrimidine derivatives to obtain highly potent and selective antagonists for the human A3 adenosine receptor.
abstract: In previous research, we identified some 7-oxo- and 7-acylamino-substituted pyrazolo[4,3-d]pyrimidine derivatives as potent and selective human (h) A3 adenosine receptor (AR) antagonists. Herein we report on the structural refinement of this class of antagonists aimed at achieving improved receptor-ligand recognition. Hence, substituents with different steric bulk, flexibility and lipophilicity (Me, Ar, heteroaryl, CH2Ph) were introduced at the 5- and 2-positions of the bicyclic scaffold of both the 7-oxo and 7-amino derivatives, and acyl residues were appended on the 7-amino group of the latter. All the 2-phenylpyrazolo[4,3-d]pyrimidin-7-amines and 7-acylamines bearing a 4-methoxyphenyl- or a 2-thienyl group at the 5-position showed high hA3 affinity and selectivity. In particular, the 2-phenyl-5-(2-thienyl)-pyrazolo[4,3-d]pyrimidin-7-(4-methoxybenzoyl)amine 25 (Ki = 0.027 nM) is one of the most potent and selective hA3 antagonists reported so far. By using an in silico receptor-driven approach the obtained binding data were rationalized and the molecular bases of the observed hA3 AR affinities were critically described.
authors.affiliation: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e salute del Bambino, sezione di Farmaceutica e Nutraceutica, Università degli Studi di Firenze, Via Ugo Schiff, 6, 50019, Sesto Fiorentino, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Squarcialupi
authors.affiliation: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e salute del Bambino, sezione di Farmaceutica e Nutraceutica, Università degli Studi di Firenze, Via Ugo Schiff, 6, 50019, Sesto Fiorentino, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Catarzi
authors.affiliation: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e salute del Bambino, sezione di Farmaceutica e Nutraceutica, Università degli Studi di Firenze, Via Ugo Schiff, 6, 50019, Sesto Fiorentino, Italy.
authors.forename: Flavia
authors.initials: F
authors.lastname: Varano
authors.affiliation: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e salute del Bambino, sezione di Farmaceutica e Nutraceutica, Università degli Studi di Firenze, Via Ugo Schiff, 6, 50019, Sesto Fiorentino, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Betti
authors.affiliation: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e salute del Bambino, sezione di Farmaceutica e Nutraceutica, Università degli Studi di Firenze, Via Ugo Schiff, 6, 50019, Sesto Fiorentino, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Falsini
authors.affiliation: Dipartimento di Scienze Mediche, Sezione di Farmacologia, Università degli Studi di Ferrara, Via Fossato di Mortara 17-19, 44121, Ferrara, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Vincenzi
authors.affiliation: Dipartimento di Scienze Mediche, Sezione di Farmacologia, Università degli Studi di Ferrara, Via Fossato di Mortara 17-19, 44121, Ferrara, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Ravani
authors.affiliation: Molecular Modeling Section (MMS), Dipartimento di Scienze del Farmaco, Università degli Studi di Padova, via Marzolo 5, 35131, Padova, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Ciancetta
authors.affiliation: Dipartimento di Scienze Mediche, Sezione di Farmacologia, Università degli Studi di Ferrara, Via Fossato di Mortara 17-19, 44121, Ferrara, Italy.
authors.forename: Katia
authors.initials: K
authors.lastname: Varani
authors.affiliation: Molecular Modeling Section (MMS), Dipartimento di Scienze del Farmaco, Università degli Studi di Padova, via Marzolo 5, 35131, Padova, Italy. Electronic address: stefano.moro@unipd.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Moro
authors.affiliation: Dipartimento di Neuroscienze, Psicologia, Area del Farmaco e salute del Bambino, sezione di Farmaceutica e Nutraceutica, Università degli Studi di Firenze, Via Ugo Schiff, 6, 50019, Sesto Fiorentino, Italy. Electronic address: vittoria.colotta@unifi.it.
authors.forename: Vittoria
authors.initials: V
authors.lastname: Colotta
mesh_terms: D058918:Adenosine A3 Receptor Antagonists / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015394:Molecular Structure; D011720:Pyrazoles / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D011743:Pyrimidines / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D043684:Receptor, Adenosine A3 / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D058918:Adenosine A3 Receptor Antagonists; D011720:Pyrazoles; D011743:Pyrimidines; D043684:Receptor, Adenosine A3; C014175:pyrazolo(3,4-d)pyrimidine
keywords: Adenosine receptor antagonists; G-protein-coupled receptors; Ligand-receptor modeling studies; Pyrazolopyrimidines