Synthesis of N6-substituted 3'-ureidoadenosine derivatives as highly potent agonists at the mutant A3 adenosine receptor.

Several N6-substituted 3 '-ureidoadenosine derivatives were efficiently synthesized starting from D-glucose for the development of H272E mutant A3 adenosine receptor (AR) agonists. Among compounds tested, 3 '-ureido-N6-(3-iodobenzyl)adenosine (2c) exhibited the highest binding affinity (Ki = 0.22 micro M) at the H272E mutant A3 AR without binding to the natural A3AR.

Probing the binding site of the A1 adenosine receptor reengineered for orthogonal recognition by tailored nucleosides.

His272 (7.43) in the seventh transmembrane domain (TM7) of the human A3 adenosine receptor (AR) interacts with the 3' position of nucleosides, based on selective affinity enhancement at a H272E mutant A3 AR (neoceptor) of 3'-ureido, but not 3'-OH, adenosine analogues. Here, mutation of the analogous H278 of the human A1 AR to Ala, Asp, Glu, or Leu enhanced the affinity of novel 2'- and 3'-ureido adenosine analogues, such as 10 (N6-cyclopentyl-3'-ureido-3'-deoxyadenosine), by >100-fold, while decreasing the affinity or potency of adenosine and other 3'-OH adenosine analogues.

Synthesis of 3'-ureidoadenosines and their high binding affinity at the mutant A3 adenosine receptor.

For the purpose of developing optimal neoceptor-neoagonist pair, 3'-ureidoadenosine derivatives were synthesized. Among compounds tested, 2-chloro-3'-ureido-N6-(3-iodobenzyl)adenosine (10b) showed the best binding affinity (Ki = 0.20 microM) at the H272E mutant A3 AR, but was inactive at the natural A3 AR.

Orthogonal activation of the reengineered A3 adenosine receptor (neoceptor) using tailored nucleoside agonists.

An alternative approach to overcome the inherent lack of specificity of conventional agonist therapy can be the reengineering of the GPCRs and their agonists. A reengineered receptor (neoceptor) could be selectively activated by a modified agonist, but not by the endogenous agonist. Assisted by rhodopsin-based molecular modeling, we pinpointed mutations of the A(3) adenosine receptor (AR) for selective affinity enhancement following complementary modifications of adenosine.

Synthesis of 3'-ureidoadenosine analogues and their binding affinity to the A3 adenosine receptor.

Novel 3'-ureidoadenosine analogues were synthesized from 1,2:5, 6-di-O-isopropylidene-D-glucose in order to lead to stronger hydrogen bonding at the A3 adenosine receptor than the corresponding 3'-aminoadenosine derivatives. However, all synthesized 3'-ureidoadenosine analogues have lost their binding affinities to the all subtypes of adenosine receptors, indicating that bulky 3'-urea moiety led to conformational distortion.