We construct the Bousfield-Kan (unstable Adams) spectral sequence based on certain nonconnective periodic homology theories E such as complex periodic K -theory, and define an E -completion of a space X . For X = S 2 n +1 and E = K we calculate the E 2 -term and show that the spectral sequence converges to the homotopy groups of the K -completion of the sphere. This also determines all of the homotopy groups of the (unstable) K -theory localization of S 2 n +1 including three divisible groups in negative stems.

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N6-Substituted 9-methyladenines are potent antagonists of the activation of A1 adenosine receptors. The present study assessed the effect of N6 and N-9 substituents on the binding of adenines to the A1 and A2 receptors, respectively, of rat brain cortex and striatum and also on the antagonism of the A2 receptor mediated stimulation of the adenylate cyclase of PC12 cells by N-ethyladenosine-5'-uronamide. The potency ranking of 9-substituted adenines varied directly with the hydrophobicity of the substituent: cyclopentyl greater than phenyl greater than tetrahydrofuryl greater than ethyl greater than methyl greater than 2-hydroxyethyl. The 9-substituted adenines showed little selectivity for either receptor and the R enantiomer of N6-(1-phenyl-2-propyl)-9-methyladenine was only 4-fold more potent than the S enantiomer at the A1 receptor. An N6-cyclopentyl substituent increased potency at the A1 receptor and decreased potency at the A2 receptor, resulting in selectivity for the A1 receptor of up to 39-fold. The N6-cyclopentyl group completely overshadowed the effect of the hydrophobicity of the 9-substituent. A 2-chloro substituent did not alter the potency of an N6-substituted 9-methyladenine.

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A Langendorff guinea pig heart preparation served for the assay of agonist potency of a series of 26 2-aralkoxyadenosines at the A1 and A2 receptors of, respectively, the atrioventricular node (conduction block) and coronary arteries (vasodilation). All of the analogues are weak agonists at the A1 receptor, requiring concentrations greater than 9 microM to cause second degree heart block. At the A2 receptor 2-phenethoxyadenosine is the most potent of the 2-phenylalkyladenosines. The activity of ring-substituted (F, Cl, CH3, and OCH3) 2-phenethoxyadenosines increases ortho less than meta less than para. The EC50s of coronary vasoactivity of several para-substituted analogues are in the subnanomolar range. The most potent analogue, 2-[2-(4-methylphenyl)ethoxy]adenosine 19, has an EC50 for coronary vasodilation of 190 pM and an A1/A2 selectivity ratio of 44,000. Aryl groups such as thienyl, indoloyl, or naphthyl also support A2 agonist activity. Although 2-oxoadenosine is 3 times more vasoactive than 2-aminoadenosine, the activities of the phenyl derivatives are markedly different; 2-phenoxyadenosine is 23 times weaker than 2-(phenylamino)adenosine (CV-1808).

The coronary vasoactivity of N-ethyl-1'-deoxy-1'-(6-amino-9H-purin-9-yl)-beta-D-ribofuranuronamide (NECA, 1) is over 2 orders of magnitude greater than that of adenosine, and the vasoactivity of certain N6-substituted adenosines is as much as 1 order of magnitude greater. Such results suggest that a combination of appropriate modifications at N6 and C-5' might additively augment the agonist potency of adenosine. At low temperatures 1-deoxy-1-(6-chloro-9H-purin-9-yl)-2',3'-O-isopropylidene- beta-D-ribofuranosyl chloride (5), obtained in three steps from inosine, reacts with amines to yield uronamides. The subsequent reaction of such uronamides with amines at elevated temperatures displaces the purine 6-chloro group to yield, after deblocking, N-alkyl(or aryl)-N6-alk(ar)yl-adenosine-5'-uronamides. At the coronary artery A2 receptor the potency of N6-modified analogues of 1 is similar to that of the N6-substituted adenosine, rather than equal to or greater than 1. As agonists in the A2 receptor-mediated stimulation of adenylate cyclase in plasma membranes of PC12 pheochromocytoma cells or human platelets, N6-substituted analogues of 1 are intermediate between the high potency of 1 and the lower potency of the N6-substituted adenosines. At the A1 receptor of rat brain the potency of an N6-substituted analogue of 1 is often greater than that of the corresponding N6-substituted adenosine. At all four receptors, replacing the ethyl group of N-ethyl-N6-3-pentyladenosine-5'-uronamide by larger alkyl groups reduces potency; amides of secondary amines are inactive or have only marginal activity. Analogues of 1 containing a chiral center in the N6 substituent retain the stereoselectivity characteristic of each of the four receptors. Thus, at either A1 or A2 adenosine receptors, adenosine analogues interact with both the N6 and the C-5' receptor regions. However, the effects of N6 and C-5' modifications on potency are less than additive, evidence that the interaction of a substituent with its receptor region influences the interaction of other substituents with their respective receptor regions.

A Langendorff guinea pig heart preparation served for the assay of agonist activity of a series of 24 2-alkoxyadenosines at the A1 and A2 adenosine receptors of, respectively, the atrioventricular node (conduction block) and coronary arteries (vasodilation). Activities are low at the A1 receptor and do not show a clear relationship to the size or hydrophobicity of the C-2 substituent. All the analogues are more potent at the A2 receptor, activity varying directly with the size and hydrophobicity of the alkyl group. The most potent analogue in this series, 2-(2-cyclohexylethoxy)adenosine has an EC50 of 1 nM for coronary vasodilation and is 8700-fold selective for the A2 receptor.