Evaluation of iodinated and brominated [11C]styrylxanthine derivatives as in vivo radioligands mapping adenosine A2A receptor in the central nervous system.

In vivo assessment of the adenosine A2A receptors localized in the striatum by PET or SPECT offers us a new diagnostic tool for neurological disorders. In the present study, we evaluated the potential of iodinated and brominated styrylxanthine derivatives labeled with 11C as an in vivo probe. [7-Methyl-11C]-(E)-3,7-dimethyl-8-(3-iodostyryl)-1-propargylxan thine ([11C]IS-DMPX) and [7-methyl-11C]-(E)-8-(3-bromostyryl)-3,7-dimethyl-1-propargylxa nthine ([11C]BS-DMPX) were prepared by the 11C-methylation of corresponding 7-demethyl derivatives. An in vitro membrane binding study showed a high affinity (Ki values) of the two ligands for A2A receptor: 8.9 nM for IS-DMPX and 7.7 nM for BS-DMPX, and a high A2A/A1 selectivity: > 1100 for IS-DMPX and 300 for BS-DMPX. In mice, [11C]IS-DMPX and [11C]BS-DMPX were taken up slightly more in the striatum than in the reference regions such as the cortex and cerebellum. The uptake ratios of striatum to cortex and striatum to cerebellum gradually increased but were very small: 1.6-1.7 for the striatum-to-cortex ratio and 1.2 for the striatum-to-cerebellum ratio at 60 min postinjection. The uptake by these three regions was reduced by co-injection of an excess amount of carrier or an A2A antagonist KF17837, but not by an A1 antagonist KF15372. The blocking effects in the three regions were greater for [11C]BS-DMPX (32-57%) than for [11C]IS-DMPX (6-29%). Ex vivo autoradiography confirmed that the two ligands were slightly concentrated in the striatum. [11C]BS-DMPX showed more selective affinity for adenosine A2A receptors than [11C]IS-DMPX, but these results have shown that the two tracers were not suitable as in vivo ligands because of low selectivity for the striatal A2A receptors and a high nonspecific binding.

Synthesis of 2-imidazolidinylidene propanedinitrile derivatives as stimulators of gastrointestinal motility--II.

In a previous paper, we reported that a novel ranitidine derivative 2 (fumarate: KW-5092), which had a 2-imidazolidinylidene propanedinitrile moiety (A), showed potent gastrointestinal motility enhancing activity. In order to obtain more potent gastrointestinal motility enhancing agents than compound 2 and to examine the effects of various substituents both at a nitrogen atom (B) in the 2-imidazolidinylidene propanedinitrile moiety and a basic nitrogen atom (C), compounds 5-29 were synthesized and evaluated for acetylcholinesterase (AChE) inhibitory activity and potentiating action on electrically stimulated contractions of guinea pig ileum. Introduction of alkyl, benzyl, aryl or acyl groups to the nitrogen (B) or (C), remarkably influenced both activities. Among these, compounds 14 and 15 showed more potent AChE inhibitory activity (IC50 = 6.7, 6.8 nM, respectively) than compound 2 and were active in potentiating action on the ileal contraction (EC30 = 9.5, 11 nM, respectively) together with a negligible histamine H2-receptor blocking property. Furthermore, these compounds were found to be more effective in the enhancement of gastrointestinal motility in anesthetized rabbits than compound 2.

Inhibitors of acyl-CoA:cholesterol acyltransferase. 1. Synthesis and hypocholesterolemic activity of dibenz[b,e]oxepin-11-carboxanilides.

A series of N-phenyl-6,11-dihydrodibenz[b,e]oxepin-11-carboxamides and related derivatives were prepared on the basis of structures of the reported inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT). These compounds were tested for their ability to inhibit ACAT (liver microsomes from cholesterol-fed rabbits) in vitro and to decrease serum total cholesterol in cholesterol-fed golden hamsters in vivo. The structure-activity relationships in vitro were as follows. Substitution at positions 2 and 6 in the anilide resulted in potent inhibitory activity, and the potency increased with increasing size of the substituents, with maximum potency being obtained with a 2,6-diisopropyl substitution. The position of the substituent on the dibenz[b,e]oxepin ring system influenced the activity, and substitution at position 2 was critical for potent activity. The electronic effect of the substituent at position 2 does not influence activity, but bulkiness seems to be a significant factor. The lipophilicity of the compounds also plays an important role in determining ACAT inhibitory activity. Among the compounds tested, 2-bromo-N-(2,6-diisopropylphenyl)-6,11-dihydrodibenz-[b,e]++ +oxepin-11- carboxamide (33, KF17828) showed significant in vitro activity (rabbit liver microsomes IC50 = 23 nM) and the most potent in vivo activity (complete reduction in elevated serum total cholesterol levels at a dose of 10 mg/kg in hamsters).

A new series of antiallergic agents. I. Synthesis and activity of 11-(2-aminoethyl)thio-6,11-dihydrodibenz[b,e]oxepin derivatives.

A new series of 11-substituted 6,11-dihydrodibenz[b,e]oxepin derivatives was synthesized and evaluated for antiallergic activity. Convenient methods for the preparation of sulfides from alcohols were developed. Structure-activity relationships are described. Compound 7, 11-[2-(dimethylamin)ethyl]thio-6,11-dihydrodibenz[b,e] oxepin-2-carboxylic acid hydrochloride, was the most potent in the rat passive cutaneous anaphylaxis test (ED50 = 0.92 mg/kg p.o.). It had a potent inhibitory effect on anaphylactic bronchoconstriction in guinea pigs (ED50 = 0.029 mg/kg p.o.) and H1 receptor antagonistic effect (Ki = 14 nM) with few central nervous system side effects. Additionally, an antagonistic effect against prostaglandin D2-induced contraction of isolated guinea pig trachea (pA2 = 5.73) was an attractive mechanism of action of the new antiallergic agent. Compound 7 was selected for further evaluation as KW-4994.

A new series of antiallergic agents. II. Synthesis and activity of new 6,11-dihydrodibenz[b,e]oxepin-carboxylic acid derivatives.

New methods for the preparation of multi-functionalized-6,11-dihydrodibenz[b,e]oxepins were developed. The structural requirements of KW-4994 (1), a promising orally active antiallergic agent, were defined. A carboxyl group at C-2 was critical for enhanced antiallergic activity of 1. The introduction of bromine atom at C-9 of 1 could elongate the duration of the action of the parent. Antiplatelet activity, a new pharmacological property of this series of compounds, was observed in one of the derivatives of 1.

Synthesis and antiarrhythmic activity of 5,11-dihydro[1]benzoxepino[3,4-b]pyridines.

During further modification of the new antiulcer agent 5 (KW-5805), a 5,11-dihydro[1]benzoxepino[3,4-b]pyridine derivative, we found that some new derivatives had antiarrhythmic activity. So we continued synthesis and evaluation of a series of 5-substituted 5,11-dihydro[1]benzoxepino[3,4-b]pyridines for antiarrhythmic activity in chloroform-induced ventricular arrhythmias in mice and in ouabain-induced ventricular arrhythmias in dogs. In chloroform-induced ventricular arrhythmias, the 7-methoxy group played an important role in activity and the type of terminal side chain at position 5 had not obvious effect on potency. On the other hand, in ouabain-induced ventricular arrhythmias, the structure-activity relationship was highly specific and only four compounds, 9, 30, 34, and 35, were effective. Compound 9,5-[[2-(diethylamino)ethyl]amino]-7-methoxy-5,11-dihydro[1] benzoxepino[3,4-b]pyridine 1.5-fumarate, which exhibited low affinity for muscarinic acetylcholine receptors and a high ED100(mydriasis)/ED50(antiarrhythmic activity) ratio, was selected for further development and clinical evaluation as KW-3407. The synthesis and antiarrhythmic activity of optically active 9 is described. The order of potency of antiarrhythmic activity in ouabain-induced ventricular arrhythmias in dogs was (-)-9, (+/-)-9, and (+)-9.

Synthesis and antiulcer activity of 5,11-dihydro[1]benzoxepino[3,4-b]pyridines.

A series of substituted 5,11-dihydro[1]benzoxepino[3,4-b]pyridines was synthesized and evaluated for antiulcer activity in water immersion/restrained stress ulcer assay in rats. Structure-activity relationships are described. Most of the tested compounds exhibited low affinity to the muscarinic acetylcholine receptor. The molecular features for the best activities are the 2-(diethylamino)ethylenediamine group at the 5-position of the oxepin ring and an oxepin skeleton rather than a thiepin or a pyran skeleton. Methyl and chlorine substitution on the benzene ring reduced the activity. Compound 11, 5-[[2-(diethylamino)ethyl]amino]-5,11-dihydro[1]benzoxepino [3,4-b]pyridine trihydrochloride was selected for further evaluation. Synthesis and antiulcer activity of optically active 11 is described. There were no statistically significant differences between (+)-, (-)-, and (+/-)-11. Compound 11 showed weak antisecretory activity in pylorus-ligated rats. It is now under clinical evaluation as KW 5805.