title: A2B adenosine receptor agonists: synthesis and biological evaluation of 2-phenylhydroxypropynyl adenosine and NECA derivatives.
abstract: In the search for agonists for the elusive A2B adenosine receptor subtypes, 2-phenylhydroxypropynyl-5'-N-methylcarboxamido adenosine (PHPMECA, 14), 2-phenylhydroxypropynyl-5'-N-propylcarboxamido adenosine (PHPPECA, 15), and N6-ethyl-2-phenylhydroxypropynyl-5'-N-ethylcarboxamidoadenosine (19) were synthesized on the basis that introduction of alkynyl chains in 2-position of adenosine derivatives resulted in reasonably good A2B potency compared to NECA [see N6-ethyl-2-phenylhydroxypropynyl adenosine (5) EC50 = 1,700 nM and 2-phenylhydroxypropynyl-5'-N-ethylcarboxamido adenosine (PHPNECA, 8) EC50 = 1,100 nM, respectively]. Radioligand binding studies and adenylyl cyclase assays, performed with recently cloned human A1, A2A, A2B, and A3 adenosine receptors, showed that these modifications produced a decrease in potency at A2B receptor, as well as a general reduction in affinity at the other receptor subtypes. On the other hand, the contemporary presence of an ethyl substituent in N6-position and of a 4'-ethylcarboxamido group in the same compounds led to (R,S)-N6-ethyl-2-phenylhydroxypropynyl-5'-N-ethylcarboxamidoadenosine and (S)-N6-ethyl-2-phenylhydroxypropynyl-5'-N-ethylcarboxamidoadenosine, which did not show the expected increase in potency at A2B subtype. Hence, (S)-2-phenylhydroxypropynyl-5'-N-ethylcarboxamidoadenosine [(S)-PHPNECA] with EC50 A2B = 220 nM remains the most potent agonist at A2B receptor reported so far.
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Camerino, Camerino (MC), Italy.
authors.forename: S
authors.initials: S
authors.lastname: Vittori
authors.forename: S
authors.initials: S
authors.lastname: Costanzi
authors.forename: C
authors.initials: C
authors.lastname: Lambertucci
authors.forename: F R
authors.initials: FR
authors.lastname: Portino
authors.forename: S
authors.initials: S
authors.lastname: Taffi
authors.forename: R
authors.initials: R
authors.lastname: Volpini
authors.forename: K N
authors.initials: KN
authors.lastname: Klotz
authors.forename: G
authors.initials: G
authors.lastname: Cristalli
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000494:pharmacology; D058908:Adenosine A2 Receptor Agonists; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D008024:Ligands; D011869:Radioligand Assay
chemical_list: C479243:2-Phenylhydroxypropynyladenosine; D058908:Adenosine A2 Receptor Agonists; D008024:Ligands; D019830:Adenosine-5'-(N-ethylcarboxamide); D000241:Adenosine