The design and synthesis of novel adenosine agonists

Synthesis of Norbornane Bisether Antibiotics via Silver-mediated Alkylation

A small series of norbornane bisether diguanidines have been synthesized and evaluated as antibacterial agents. The key transformation-bisalkylation of norbornane diol 6-was not successful using Williamson methodology but has been accomplished using Ag2O mediated alkylation. Further functionalization to incorporate two guanidinium groups gave rise to a series of structurally rigid cationic amphiphiles; several of which (16d, 16g and 16h) exhibited antibiotic activity. For example, compound 16d was active against a broad range of bacteria including Pseudomonas aeruginosa (MIC = 8 µg/mL), Escherichia coli (MIC = 8 µg/mL) and methicillin-resistant Staphylococcus aureus (MIC = 8 µg/mL).

Geometry, topology, and atom-weights assembly descriptors to predicting A1 adenosine receptors agonists

The GEometry, Topology, and Atom-Weights AssemblY (GETAWAY) approach has been applied to the study of the A1 adenosine receptors agonist effect of 32 adenosine analogues: N6-arylcarbamoyl, 2-arylalkynyl-N6-arylcarbamoyl, and N6-carboxamido derivatives. A model, able to describe more than 77% of the variance in the experimental activity, was developed with the use of the above mentioned approach. Five different approaches (Topological, Galvez Topological Charges indexes, Randic Molecular Profiles, Geometrical, and WHIM descriptors) failed to give satisfactory models (R2=0.70) for this property with the same number of variables in the equation. Although statistically significant models were derived containing descriptors other than GETAWAY, the best fitted out model was still found with these descriptors.

New potent and selective A1 adenosine receptor agonists

Thiirane analogs of ENAdo have been synthesised and found to be extremely potent and selective A(1) adenosine receptor agonists.

New 2,N6-disubstituted adenosines: potent and selective A1 adenosine receptor agonists

A number of adenosine analogues substituted in the 2- and N6-positions were synthesized and evaluated for affinity, functional potency and intrinsic activity at the A1 and A2A adenosine receptors (AR). Three classes of N6-substituents were tested; norbornen-2-yl (series 1), norborn-2-yl (series 2) and 5,6-epoxynorborn-2-yl (series 3). The halogens; fluoro, bromo, and iodo were evaluated as C-2 substituents. All compounds showed relatively high affinity (nanomolar) for the A1AR and high potency for inhibiting (-)isoproterenol-stimulated cAMP accumulation in hamster smooth muscle DDT1 MF-2 cells with the 2-fluoro derivatives from each series having the highest affinity. All of the derivatives showed the same intrinsic activity as CPA. At the A2AAR, all of the derivatives showed relatively low affinity and potency (micromolar) for stimulating cAMP accumulation in rat pheochromocytoma PC-12 cells. The intrinsic activity of the derivatives compared to CGS 21680 was dependent upon the halogen substituent in the C-2 position with most showing partial agonist activity. Of particular interest is 2-iodo-N6-(2S-endo-norborn-2-yl)adenosine (5e), which is over 100-fold selective for the A1AR, is a full agonist at this receptor subtype and has no detectable agonist activity at the A2AAR.

Adenosine receptor ligands with oxygenated N6-substituents

A number of novel adenosine analogs bearing oxygenated substituents in the N6-position have been prepared and evaluated as A1 adenosine agonists. Improved conditions for the synthesis of N6-substituted adenosines and a new one pot procedure for the synthesis of 2-amino-7-oxabicyclo[2.2.1]hept-5-ene are also reported.

N6-(5,6-epoxynorbornyl)adenosine analogs as A1 adenosine agonists

A range of related adenosines and 5'-N-ethylcarboxamidoadenosines bearing oxygenated substituents in the N6 position have been synthesised and evaluated as A1-adenosine receptor ligands. Compound 9 emerged with potent affinity (EC50 = 1.1 nM).

Synthesis and biological evaluation of the enantiomers of the potent and selective A1-adenosine antagonist 1,3-dipropyl-8-[2-(5,6-epoxynorbonyl)]-xanthine

The individual enantiomers 8 and 12 of the potent and highly selective racemic A1-adenosine antagonist 1,3-dipropyl-8-[2-(5,6-epoxynorbornyl)]xanthine (ENX, 4) were synthesized utilizing asymmetric Diels-Alder cycloadditions for the construction of the norbornane moieties. The absolute configuration of 12 was determined by X-ray crystallography of the 4-bromobenzoate 14, which was derived from the bridged secondary alcohol 13. The latter was obtained from 12 by an acid-catalyzed intramolecular rearrangement. The binding affinities of the enantiomers 8 and 12 and the racemate 4 at guinea pig, rat, and cloned human A1- and A2a-adenosine receptor subtypes were determined. The S-enantiomer 12 (CVT-124) appears to be one of the more potent and clearly the most A1-selective antagonist reported to date, with K1 values of 0.67 and 0.45 nM, respectively, at the rat and cloned human A1-receptors and with 1800-fold (rat) and 2400-fold (human) subtype selectivity. Both enantiomers, administered intravenously to saline-loaded rats, induced diuresis via antagonism of renal A1-adenosine receptors.