Synthesis and serotonin 2 (5-HT2) receptor antagonist activity of 5-aminoalkyl-substituted pyrrolo[3,2-c]azepines and related compounds

A series of 5-aminoalkylpyrrolo[3,2-c]azepine derivatives was synthesized and their serotonin 2 (5-HT2) receptor antagonist and antiplatelet aggregation activities were evaluated. 5-HT2 receptor antagonist activity was largely determined by the nature of the substituent at the 8-position as well as the aminoalkyl group at the 5-position of the pyrrolo[3,2-c]azepine ring. Compound 18a, 5-[3-[4-(4-fluorophenyl)piperazin-1-yl]propyl]-8-hydroxy-1-methyl- 1,4,5,6,7,8-hexahydropyrrolo[3,2-c]azepin-4-one, was recognized as having potent 5-HT2 receptor antagonist activity with weak alpha1 adrenoceptor blocking activity and no significant D2 receptor binding affinity, while the corresponding isomeric pyrrolo[3,4-c]azepine derivative (22) displayed only weak 5-HT2 receptor antagonist activity. After racemic 18a was resolved directly via diastereomeric salt formation, each enantiomer was evaluated precisely. The 5-HT2 receptor antagonist activity of 18a was found to reside primarily in (-)-18a (which was about 14-fold more potent than (+)-18a in isolated guinea pig arteries). Consequently, (S)-(-)-18a (SUN C5174) displayed the overall best profile with potent 5-HT2 receptor antagonist activity (pA2=8.98+/-0.06) and high selectivity versus other receptors. SUN C5174 showed a marked inhibitory effect on the platelet aggregation induced by serotonin in combination with collagen and adenosine diphosphate (ADP) in canine or human platelet-rich plasma (IC50=6.5 to 16 nM). Moreover, this compound significantly inhibited the mortality rate in mouse acute pulmonary thromboembolytic death induced by collagen and serotonin at oral doses of 0.3 mg/kg or higher. SUN C5174 is currently undergoing clinical evaluation.     

Synthesis and antitumor activity of 7-(N-glycosylamino)-indolo[3,2-b]quinolines

Novel indolo[3,2-b]quinolines (1d-g), introduced at the 7-position with an N-glycosylamino group, were prepared and their antitumor activities against leukemia P388 in mice were examined. The N-Galactopyranosylamino derivative (1e) was a much more potent anti-leukemia compound (optimal dose = 25 mg/kg, T/C greater than 333%, cure 5/6) than lead compound 1a.     

Synthesis and evaluation of carbamate prodrugs of a phenolic compound

A series of carbamates of the phenolic compound 1 were prepared and evaluated in vivo as its prodrug. Each carbamate was orally administered to rats, and plasma concentrations of the parent compound 1 were measured with the passage of time. We judged which carbamate was suitable for the prodrug of 1 from both the AUC value of 1 and absence of the carbamate in plasma. The AUC value of 1 after oral administration of 2b was approximately 40-fold higher than that for an administration of 1, and the bioconversion from 2b to 1 was excellent. As a whole, di-substituted carbamates resulted in higher plasma concentrations of 1 than did mono-substituted ones. However di-substituted carbamates were almost always detected in plasma. As a result, we found that the ethycarbamoyl derivative 2b demonstrates the best prodrug property in this series.     

Synthesis of 11β-ether-17α-ethinyl-3,17β-estradiols with strong ER antagonist activities

We have previously found that several families of nonpolar short chain 11 β-ethers and esters of estradiol are selective estrogen receptor modulators(SERMs).Surprisingly,the transformation from potent estrogen to anti-estrogen occurs when the 11β-side chain is increased slightly in length from four to five non-hydrogen atoms.To generate strong antagonists for preclinical development,we have synthesized other similar ER ligands with 11β-ethers and with an additional ethinyl group at the 17α-position in order to slow metabolism of the steroidal moiety.Here we report the synthesis and biological activity of two such compounds(11β-i-PrO-propyl and 11β-t-BuO-propyl ethers) with extremely strong antagonist activities.     

Studies on antihypertensive agents with antithrombotic activity. 2. Syntheses and pharmacological evaluation of pyrrolo[2,3-c]azepine derivatives

As an extension of our previous investigation, a series of 7-aminoalkylpyrrolo[2,3-c]azepine derivatives was synthesized and evaluated as alpha1-adrenergic- and serotonin 2 (5-HT2)-receptor antagonists, with the aim of finding a novel potent antihypertensive agent with both activities. Among the compounds obtained in this study, (E)-1-ethyl-7-[3-[4-(4-fluorophenyl)piperazin-1-yl]propyl]-4-hy droxyimino-1,4,5,6,7,8-hexahydropyrrolo[2,3-c]azepin-8-on e (16d) displayed potent alpha1-adrenoceptor blocking activity (pA2=7.83+/-0.20) and 5-HT2-receptor blocking activity (pA2=9.47+/-0.17) in isolated guinea pig arteries. At 3 mg/kg oral administration, compound 16d exhibited antihypertensive activity more potent than that of doxazosin in deoxycorticosterone acetate (DOCA)-salt hypertensive dogs. Furthermore, this compound reduced the rate of mouse acute pulmonary thromboembolytic death induced by collagen and serotonin at oral doses of 0.3 mg/kg or more, and its effect lasted for at least 6 h at 3 mg/kg.     

A novel class of platelet activating factor (PAF) antagonists. II. Modification of the 2-position of the glycerol backbone of PAF-sulfonamide isosteres.

In a continuing effort to obtain more potent platelet activating factor (PAF) antagonists, we tried to synthesize a series of PAF-sulfonamide isosteres in which the substituent at the 2-position was modified to an acetoxy equivalent other than the methoxy group. These modifications produced highly active PAF antagonists. Compound 3-[2-(5-methyl-2H-tetrazol-2-yl)-3-(octadecylcarbamoyloxy) propylaminosulfonyl]propylquinolinium iodide (52) showed the most potent activity in the in vitro inhibitory effect on PAF-induced platelet aggregation in rabbit platelet-rich plasma (IC50 = 125 nM) and also in the in vivo protective effect on PAF-induced lethality in mice, with prolonged duration of action. Optically active enantiomers of this compound were synthesized and the (S)-(-)-isomer (IC50 = 87 nM) was found to be three times more potent that the (R)-(+)-isomer (IC50 = 289 nM), clearly exemplifying the enantioselectivity in the PAF-antagonist action of this novel compound.     

Antifolate chemistry: synthesis of 4-[N-[(6RS)-2-methyl-4-oxo-3,4,7,8-tetrahydro-6H-cyclopenta[g]quinazolin-6-yl]-N-(prop-2-ynyl)amino]benzoic acid via a (propargyl)Co2(CO)6+ complex

A new route to compound 3 (4-[N-(6RS)-2-methyl-4-oxo-3,4,7,8-tetrahydro-6H-cyclopenta[g]quinazolin-6-yl]-N-(prop-2-ynyl)amino]benzoic acid), a crucial intermediate for the synthesis of potent inhibitors of thymidylate synthase (TS), is described. In this sequence the C6-N10 bond was constructed first, by the reductive amination of 5-acetamido-6-bromoindan-1-one 6 with tert-butyl 4-aminobenzoate, then the cyclopenta[g]quinazolinone ring was formed and the propargyl group was introduced on the N10-position using the (propargyl)Co2(CO)6+ complex as the electrophilic propargyl reagent.     

Biosynthesis of lipstatin. Incorporation of multiply deuterium-labeled (5Z,8Z)-tetradeca-5,8-dienoic acid and octanoic acid.

Fermentation experiments with Streptomyces toxytricini were performed using (5Z,8Z)-[10,11,12,12-(2)H]tetradeca-5,8-dienoic acid or a mixture of [2,2-(2)H(2)]- and [8,8,8-(2)H(3)]octanoic acid as supplements. (2)H NMR and mass spectroscopy confirmed the incorporation of (5Z,8Z)-[10,11,12,12-(2)H]tetradeca-5,8-dienoic acid into the C(13) side chain as well as into the C(6) side chain of lipstatin. Moreover, deuterium was incorporated into the C(6) side chain of lipstatin from the 8-position but not from the 2-position of octanoate. The data establish that the beta-lactone moiety of lipstatin is formed by condensation of a C(8) and a C(14) fatty acid with a concomitant exchange of the H-2 atoms of the C(8) fatty acid.     

2-(O-Phenylalkyl)phenoxy]alkylamines III: Synthesis and selective serotonin-2 receptor binding (2)

A series of 12-(2-phenylethyl)phenoxy]ethylpyrrolidine derivatives were synthesized, and their affinity for serotonin-2 (5-HT2) and dopamine-2 (D2) receptors was examined. Among them, compound 17, (2R,4R)-4-hydroxy-2-[2-[2-[2-(3-methoxyphenyl)ethyl]phenoxylethyl] -1-methylpyrrolidine hydrochloride, showed high 5-HT2 receptor affinity in vitro. This compound was a more potent inhibitor of ex vivo 5-HT-induced platelet aggregation than compound 3, which was previously shown to be more potent than ketanserin (1) and sarpogrelate (2a). However, compound 17 produced gastric irritation in rats. Therefore, we carried out a further derivatization of 17, and compound 45 (R-102444), a lauryl ester prodrug of compound 17, was found to be a promising candidate as an antithrombotic agent. Oral administration of R-102444 produced a marked inhibition of 5-HT-induced ex vivo platelet aggregation, and R-102444 did not cause any gastric irritation. The antiaggregatory effects of R-102444 were more potent than those of sarpogrelate (2a) and its active metabolite, M-1 (2b). In addition, R-102444 exhibited more potent antithrombotic effects than sarpogrelate in a rat photochemically-induced thrombosis model.     

Orally active CCR5 antagonists as anti-HIV-1 agents: synthesis and biological activity of 1-benzothiepine 1,1-dioxide and 1-benzazepine derivatives containing a tertiary amine moiety

The search for orally active CCR5 antagonists was performed by chemical modification of the 1-benzothiepine 1,1-dioxide 3 and 1-benzazepine 4 lead compounds containing a tertiary amine moiety. Replacement of methyl group with a 2-(C(2-4) alkoxy)ethoxy group at the 4-position on the 7-phenyl group of the 1-benzothiepine ring resulted in both enhanced activity and significant improvement in the pharmacokinetic properties upon oral administration in rats. Introduction of C(2-4) alkyl, phenyl or (hetero)arylmethyl groups as the 1-substituent on the 1-benzazepine ring together with the 2-(butoxy)ethoxy group led to further increase of activity. Among the 1-benzazepine derivatives, the isobutyl (6i), benzyl (6o) or 1-methylpyrazol-4-ylmethyl (6s) compounds were found to exhibit highly potent inhibitory effects, equivalent to the injectable CCR5 antagonist 1, in the HIV-1 envelope-mediated membrane fusion assay. In particular, compound 6s showed the most potent CCR5 antagonistic activity (IC(50)=2.7 nM) and inhibitory effect (IC(50)=1.2 nM) on membrane fusion, together with good pharmacokinetic properties in rats. The synthesis of 1-benzothiepine 1,1-dioxide and 1-benzazepine derivatives and their biological activity are described.     

A novel class of platelet activating factor (PAF) antagonists. I. Synthesis and structure-activity studies on PAF-sulfonamide isosteres.

New platelet activating factor (PAF) antagonists, 3 were synthesized by replacing the charged phosphate and trimethylammonium moieties with sulfonamide and heterocyclic quaternary ammonium functionalities, respectively (PAF-sulfonamide isosteres). Darmstoff phosphatidic acid analogues of this class (Darmstoff-sulfonamide isosteres), 6 were also synthesized. The activity of these compounds as PAF antagonists was evaluated from their in vitro inhibitory effect on PAF-induced platelet aggregation in rabbit platelet-rich plasma. Among the compounds tested, some of the 2-methoxypropane derivatives with an octadecylcarbamoyloxy or octadecylcarbamoylthio side chain at the 1-position and a propylsulfonamide function bearing a terminal polar substituent such as a quaternary quinolinium or substituted quinolinium group at the 3-position were found to be the most potent (IC50 = 0.3-0.6 microM).     

Imidazo[1,2-a]pyridines. I. Synthesis and inotropic activity of new 5-imidazo[1,2-a]pyridinyl-2(1H)-pyridinone derivatives

A series of 1,2-dihydro-5-imidazo[1,2-a]pyridinyl-2(1H)-pyridonones was synthesized and evaluated for positive inotropic activity, 1,2-Dihydro-5-imidazo[1,2-a]pyridin-6-yl-6-methyl-2- oxo-3-pyridinecarbonitrile (11a) hydrochloride monohydrate (E-1020) was found to be a potent and selective inhibitor of phosphodiesterase III and a long-acting, potent, orally active positive inotropic agent. Additional imidazo[1,2-a]pyridin-2-yl (3a), -3-yl (16), -7-yl (20) and -8-yl (24a) compounds were also prepared. Altering the pyridine substitution from the 2-position to the 6-position produced a 2-fold increase in the i.v. cardiotonic potency (ED50) from 52 to 23 micrograms/kg, while substitution at the 3-, 7- or 8-position reduced potency. In the 2-positional isomers, introduction of halogen groups enhanced the activity and 3-chloro-1,2-dihydro-5-(6-fluoroimidazo[1,2-a] pyridin-2-yl)-6-methyl-2(1H)-pyridinone (3u) was the most potent (i.v. ED50 11 micrograms/kg) in this series. E-1020 is presently under development for the treatment of congestive heart failure.     

Structure-activity relationships of 6-nitroquinazolines: dual-acting compounds with inhibitory activities toward both TNF-alpha production and T cell proliferation

We synthesized various 6-nitroquinazolines by modifying the structure of compound 1 and evaluated their inhibitory activities toward both TNF-alpha production and T cell proliferation responses. The presence of the unsubstituted piperazine ring at the C(7)-position was required for both inhibitory activities. In this series of compounds, 5d and 5f, containing the 4-fluorophenyl and 3,4-difluorophenyl moiety, respectively, at the C(4)-position, showed the suppressing effects toward both responses with low cell growth inhibition. Furthermore, the oral administration of these compounds mentioned above at doses of 30 and 100 mg/kg also resulted in significant inhibition of TNF-alpha production induced by LPS in vivo.     

Synthesis and antitumor activity of fused quinoline derivatives. II. Novel 4- and 7-hydroxyindolo-[3,2-b]quinolines.

Novel indolo[3,2-b]quinoline derivatives (1c--f), which carried a methoxy or a hydroxy group at the 4- or 7-position of the lead compound 1a, were prepared and their antitumor activities against P388 in mice were examined. Except for the 4-hydroxy derivative (1d), these showed remarkably potent activity. Among these compounds, the 7-hydroxy derivative (1f) was the most potent one (optimal dose = 50 mg/kg, the median survival time of treated group/control group (T/C) greater than 330%, cure = 5/6).     

Discovery of a novel and potent human and rat beta3-adrenergic receptor agonist, [3-[(2R)-[[(2R)-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]-1H-indol-7-yloxy]acetic acid

In search for potent and selective beta3-adrenergic receptor (beta3-AR) agonists as potential drugs for the treatment of type II diabetes and obesity, a novel series of 1-(3-chlorophenyl)-2-aminoethanol derivatives were prepared and evaluated for their biological activity at human beta1-, beta2-, and beta3-ARs and rat beta3-AR expressed in Chinese hamster ovary (CHO) cells. Replacement of the right-hand side (RHS, benzene ring) in the 'first generation' beta3-AR agonists BRL 37344 and CL 316243 with a 1H-indole ring gave compound 31 with unique pharmacological properties among beta3-AR agonists. Initial in vitro assays showed that 31 possesses modest rat and human beta3-ARs agonistic activity. Introduction of various substituent into the indole nucleus of 31 afforded a number of compounds with good beta3-ARs agonistic activity. In particular, 90 having a carboxylic acid functionality at the 7-position of the indole nucleus showed the most potent human beta3-AR agonistic activity. Finally, optical resolution of 90 led to the identification of the most promising compound, [3-[(2R)-[[(2R)-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]-1H-indol-7-yloxy]acetic acid (96, AJ-9677). This compound exhibited potent human beta3-AR agonistic activity (EC50=0.062 nM, IA=116%) with 210- and 103-fold selectivity over human beta2-AR and beta1-AR, respectively. Compound 96 also exhibited potent rat beta3-AR agonistic activity (EC50=0.016 nM, IA=110%). Moreover, repeated oral administration of 96 inhibited body weight gain and significantly decreased glucose, insulin, free fatty acid, and triglyceride concentrations in plasma in KK-Ay/Ta mice. On the basis of this pharmacological profile, 96 entered clinical development as a drug for the treatment of type II diabetes and obesity.     

Synthesis of 2-guanyl-4-(3-substituted-phenyl)thiazoles with potent histamine H2-antagonism activity

The syntheses of novel 2-guanyl-4-(3-substituted-phenyl)thiazoles showing potent histamine H ₂-antagonism activity is reported. The most potent compound is 17 where the substitution at the 3-position of the phenyl ring is an N-methylamidino function.     

Multigram-scale syntheses, stability, and photoreactions of A2A adenosine receptor antagonists with 8-styrylxanthine structure: potential drugs for Parkinson's disease

The improved multigram-scale syntheses of the important 8-styrylxanthine A(2A) adenosine receptor antagonist MSX-2 (8), its water-soluble prodrug MXS-3 (9), and KW-6002 (16) are described. N-Alkylation reactions at different positions of uracil derivatives were optimized. Two different methods for xanthine formation from 6-amino-5-cinnamoylaminouracil precursors were investigated, (a) the elimination of water by alkaline catalysis and (b) hexamethyldisilazane as a condensing agent; the latter was found to be superior. The photosensitivity of 8-styrylxanthines was studied. The (E)-configurated stryrylxanthine MSX-2 (8) isomerized in diluted solution, and the resulting (Z)-isomer (10a) was isolated and characterized. Furthermore, we describe for the first time that solid 8-styrylxanthines can dimerize upon exposition to daylight or irradiation with UV light. The resulting cyclobutane derivatives with head-to-tail (syn) configuration exhibited a considerably lower A(2A) adenosine receptor affinity than their parent compounds. The dimerization product of MSX-2 was a moderately potent nonselective A(1) and A(2A) antagonist (K(i)(A(1)) = 273 nM, K(i) (A(2A)) = 175 nM) while the dimer of the related compound KW-6002 was inactive at A(1) and only weakly active at A(2A) adenosine receptors (K(i) = 1.57 microM). The light sensitivity of 8-styrylxanthine derivatives, not only in solution, but also in the solid state, has to be considered when using those compounds as pharmacological tools or drugs.     

Studies on topical antiinflammatory agents. III. Synthesis of 17 alpha-acyloxy-9 alpha-fluoro-11 beta-hydroxy-16 beta-methyl-1,4-pregnadiene-3,20-dione 21-thio derivatives and related compounds

A series of 21-thio derivatives of 9 alpha-fluoro-11 beta,17 alpha-dihydroxy-16 beta-methyl-1,4-pregnadiene-3, 20-dione 17-esters and related compounds were synthesized and evaluated as topical antiinflammatory agents. These compounds were prepared by the reaction of 9 alpha-fluoro-11 beta,17 alpha,21-trihydroxy-16 beta-methyl-1,4-pregnadiene-3, 20-dione (betamethasone, I) 17-ester derivatives and various mercapto compounds. A structure-activity relationship study revealed that the structural combination of a thio group at the 21-position and an ester group at the 17-position contributed to vasoconstrictive activity. Among these compounds, the 21-methylthio 17-propanoate compound (6) was found to have the most potent activity, being more potent than betamethasone 17-valerate (BV).     

An efficient synthesis of 5-bromo-2-methoxy-6-methylaminopyridine-3carboxylic acid

An efficient synthesis of 5-bromo-2-methoxy-6-methylaminopyridine-3-carboxylic acid (1), a carboxylic acid moiety of a potent dopamine D2 and D3 and serotonin-3 (5-HT3) receptors antagonist, (R)-5-bromo-N-(1-ethyl-4-methylhexahydro-1 ,4-diazepin-6-yl)-2-methoxy-6-methylaminopyridine-3-carboxamide, is described. Reaction of methyl 2,6-difluoropyridine-3-carboxylate (12) with methylamine in EtOH at -25 degrees C gave a mixture of methyl 2-fluoro-6-methylaminopyridine-3-carboxylate (13) and the regioisomer 14 in a ratio of 57 : 43. On the other hand, reaction of 12 and methyl 2,6-dichloropyridine-3-carboxylate (16) with sodium methoxide in tetrahydrofuran (THF) and CH2Cl2 provided the 2-methoxypyridine-3-carboxylic esters 20 and 23, respectively, as main products. Similar reaction of 16 in N,N-dimethylformamide (DMF) and MeOH proved to be highly regioselective for the 6-position. A much greater regioselectivity for substitution at the 6-position (>97%) was observed when 16 was treated with 4-methylbenzenethiolate anion in DMF (quantitative yield). After methoxylation of methyl 2-chloro-6-(4-methylbenzenethio)pyridine-3-carboxylate (25b) and successive oxidation of the 6-benzenethio moiety, nucleophilic substitution of the sulfoxide derivative 28 with methylamine gave the 6-methylamino derivative 8. Finally, bromination of 8 and alkaline hydrolysis produced the desired product 1 in an overall yield of 67%.