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Nortopsentins A-D, antifungal 1, 4-bisindolylimidazole marine alkaloids isolated from a sponge, were synthesized through palladium-catalyzed cross-coupling of 3-indolylboronic and 6-bromo-3-indolylboronic acids with halogenoimidazoles as the key reaction.

Trimethylsilylaion of 1, 2, 3-triazole regioselectively proceeded to give 2-trimethylsilyl-2H-1, 2, 3-triazole, which was treated with primary alkyl halides in the presence of tetrabutylammonium fluoride to give 1-alkyl-1H-1, 2, 3-triazoles as a sole product. 1-Methyl-5-substituted 1H-1, 2, 3-triazoles were prepared by alkylation of 5-lithio-1-methyl-1H-1, 2, 3-triazole, and 1-methyl-4-substituted 1H-1, 2, 3-triazoles were obtained by alkylaiton of 4-lithio-1-methyl-5-phenylthio-1H-1, 2, 3-triazole followed by reductive desulfurization.

In the presence of samarium diiodide, 2-aryl and 2-heteroaryl cyclopropane-1, 1-dicarboxylic esters were readily dimerized to give 3, 4-disubstituted 1, 1, 6, 6-hexanetetracarboxylic esters as diastereomeric mixtures in moderate to good yields. The diastereomeric mixtures were separated by preparative HPLC and stereo-chemistries of the isolated meso and racemic compounds were determined on the basis of HPLC analysis on chiral stationary phases. Between the 1H-NMR spectra of the separated diastereomers, the characteristic differences in the chemical shifts of the C2-H (C5-H) signals were observed and explained based on the MOPAC calculation.

The first total synthesis of clathridine A (8), a marine imidazole alkaloid, was achieved by using a novel regioselective condensation as a key step, in which preclathridine A (2) was treated with 1-methylparabanic acid (11) in the presence of a silylating agent.

Treatment of 1,3-dialkyl-2-(phenylthio)benzimidazolium salts 3 and 1,3-dialkyl-2-phenylthio-1H-imidazolium salts 7 with aq. K2CO3 gives 1,3-dialkyl-1,3-dihydrobenzimidazol-2-ones 4 and 1,3-dialkyl-1,3-dihydroimidazol-2-ones 8, respectively, in 22–94% yield. A regio-isomer 17 of kealiiquinone, a marine benzimidazole alkaloid, where the 4-methoxyphenyl group at the 4-position migrates to the 9-position, is synthesized by application of the reaction. Cytotoxity of 17 and kealiiquinone against 39 human cancer cells is evaluated. They have weak activity but a unique mechanism of action.

Diels–Alder-type dimerization of various 5-ethenyl-2-phenylsulfanyl-1 H -imidazoles provided a novel highly regio- and stereoselective route to the preparation of multifunctionalized 4,5,6,7-tetrahydrobenzimidazoles, the basic skeleton of ageliferin, a biologically active pyrrole–imidazole marine alkaloid. The reaction was applied to the synthesis of 12,12′-dimethylageliferin.

Several 1-alkoxy-2,3-dichloro-4-hydroxynaphthalene derivatives were prepared. These compounds were oxidized by hydrogen peroxide in the presence of a peroxidase to give 2,3-dichloro-1,4-naphthoquinone, which then reacted with various alkyl benzoylacetates to develop blue coloration with absorption maximum at greater than 600 nm. The color development reaction can be applied to the determination of appropriate serum constituents such as cholesterol.

Eleven 3-substituted isocoumarins and a benzylidenephthalide were synthesized through thermal cyclization reaction of δ- and γ-ketoamides, respectively. Subsequent deprotection of the hydroxyl groups of the resulting isocoumarin and benzylidenephthalide compounds afforded thunberginols A, B, and F, respectively, which originated from the processed leaves of Hydrangea macrophylla SERINGE var. thunbergii MAKINO. The synthesized isocoumarins and thunberginols were evaluated for their anti-allergic activity, in which thunberginol B exhibited the highest inhibitory potency on the degranulation of RBL-2H3 cells induced by antigen. Structure–activity relationship studies were carried out to determine the necessary substituents on the 3-phenylisocoumarin skeleton for inhibitory activity.

We found two novel skeleton rearrangement reactions. The one was the reaction from coumarin derivatives having an electron-withdrawing group at the 3-position with dimethylsulfoxonium methylide to cyclopenta[b]benzofuran derivatives. The other was the reaction from benzo[b]cyclobuta[d]pyran derivatives having an electron-withdrawing group at the 2a-position to tetrahydrodibenzofuran derivatives. Interestingly, the latter reaction proceeded stereoconvergently regardless of the stereochemistry at the 1-position in the cyclobutane compounds. Driving forces of these reactions would be attributable to release of the ring strain including in a cyclopropane ring and cyclobutane ring. These methodologies were applied to the total synthesis of linderol A, which is a constituent of Lindera umbellata (Lauraceae) and has a potent inhibitory activity on melanin biosynthesis, and the synthesis was performed in 14 steps, 34% overall yield. Furthermore, the uncertain absolute structure of linderol A was determined, and its asymmetric synthesis was also achieved.

The novel skeleton transformation reaction of 2a-substituted 2a,8b-dihydrobenzo[ B]cyclobuta[ D]pyran-3-one derivatives into 2-(2-substituted 2-oxoethyl)-2 H-1-benzopyran derivatives has been accomplished using Znl 2 in the presence of an organic base and water in excellent yields.

Several 2-alkylcarbamoyl-1-alkylvinylbenzo[b]furans were designed to find a selective leukotriene B4 (LTB4) receptor antagonist. 2-(2-Alkylcarbamoyl-1-alkylvinyl)benzo[b]furans having a substituent group at the 3-position, 4-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans having a substituent group at the 3-position, and 7-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans and 3-(2-alkylcarbamoyl-1-alkylvinyl)benzo[b]furans were prepared and evaluated for LTB4 receptor (BLT1 and BLT2) inhibitory activities. (E)-3-Amino-4-[2-[2-(3,4-dimethoxyphenyl)ethylcarbamoyl]-1-methylvinyl]benzo[b]furan ((E)-17c) showed potent and selective inhibitory activity for BLT2. On the other hand, (E)-7-(2-diethylcarbamoyl-1-methylvinyl)benzo[b]furan ((E)-27a) showed potent inhibitory activity for both BLT1 and BLT2.

2-ethenyl-1H-imidazoles 6 were readily prepared by treating 2-(1-hydroxyalkyl)-1H-imidazoles 5 with hot acetic anhydride. Several convenient procedures to precursors of 6 are described

5-Methyl-7, 8, 9, 10-tetrahydro-5H-azepino[1, 2-α]benzimidazol-7-one (6) was synthesized by treating 1-(3-carboxypropyl)-2, 3-dimethylbenzimidazolium iodide (11) with 1, 1'-carbonyldiimidazole in the presence of triethylamine. Refluxing 2-(5-chloro-2-oxopentyl)-1-methylbenzimidazole (4) in ethyl acetate did not afford 6 but gave (Z)-1-methyl-2-(2, 3, 4, 5-tetrahydro-2-furylidenemethyl)benzimidazole (5), which was rearranged to the corresponding (E)-isomer (7) by heating in ethyl acetate in the presence of basic alumina. The structures of 5, 6 and 7 were determined by X-ray crystallography.

Head-to-head photo[2+2]cycloaddition of 1, ω -di[3-(1-methyl-2-phenylsulfanyl-1H-imidazol-5-yl)propenoyloxy]alkylenes smoothly proceeded under irradiation of a high-pressure mercury lamp to give cyclobutane compounds regio- and stereoselectively. The stereochemistry of these cyclobutanes was determined as β-form.

5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO), a new cyclic DEPMPO-type nitrone was evaluated for spin-trapping capabilities toward hydroxyl and superoxide radicals. CYPMPO is colorless crystalline and freely soluble in water. Both the solid and diluted aqueous solution did not develop electron spin resonance (ESR) signal for at least 1 month at ambient conditions. CYPMPO can spin-trap superoxide and hydroxyl radicals in both chemical and biological systems, and the ESR spectra are readily assignable. Half life for the superoxide adduct of CYPMPO produced in UV-illuminated hydrogen peroxide solution was approximately 15 min, and in biological systems such as hypoxanthine (HX)/xanthine oxidase (XOD) the half-life of the superoxide adduct was approximately 50 min. In UV-illuminated hydrogen peroxide solution, there was no conversion from the superoxide adduct to the hydroxyl adduct. Although overall spin-trapping capabilities of CYPMPO are similar to DEPMPO, its high melting point, low hygroscopic property, and the long shelf-life would be highly advantageous for the practical use.

Stereoselective preparation of 1-exo-substituted 1,2,2a,8b-tetrahydro-3H-benzo[b]cyclobuta[d]pyran-3-ones (2) was achieved by photo [2+2] cycloaddition of olefins to 3-substituted coumarins (1). 1-endo-Substituted 1,2,2a,8b-tetrahydro-3H-benzo[b]cyclobuta[d‖pyran-3-ones (3) were stereoselectively prepared by hydrogenation over the Pd-carbon of 2a,8b-dihydro-3H-benzo[b]cyclobuta[d]pyran-3-ones (5), which were obtained by photo [2+2] cycloaddition of the coumarins (1) to acetylenes. The stereochemistry of 1-exo- and 1-endo-arylcyclobutanes (2 and 3) could be easily determined on the basis of the 1 H-NMR spectrum, in which the C8-proton in 3 was strongly shielded by the 1-aryl ring but that in 2 was not.

We have developed efficient catalytic methods for the stereoselective and diversity synthesis of various (E)-, (Z)-, and disubstituted 3-alkylideneoxindoles and 3-alkylidenebenzofuran-2-ones via palladium-catalyzed Heck/Suzuki−Miyaura, Heck/Heck, and Heck/carbonylation/Suzuki−Miyaura domino reactions.

1,2a-Disubstituted 1,2,2a,8b-tetrahydro-3H-benzo[b]cyclobuta[d]pyran-3-ones (10) bearing an electron-withdrawing group at the 2a-position were treated with two equivalents of dimethylsulfoxonium methylide to give r-1,t-4a,t-9b-1,3-disubstituted 1,2,4a,9b-tetrahydrodibenzofuran-4-ols (11) stereoconvergently regardless of the stereochemistry of the 1-position on the benzocyclobutapyran ring. This methodology was applied to the second-generation synthesis of (±)-linderol A (12), a melanin biosynthesis inhibitory natural product.

A novel task-specific ionic ligand with an imidazolium salt moiety was synthesized, and its catalytic ability and recyclability for asymmetric transfer hydrogenation of acetophenone derivatives with a formic acid–triethylamine azeotropic mixture in an ionic liquid [bmim][PF6] was examined.

Racemic triol 4-acetyl-3,6-dihydroxy-6-hydroxymethyl-1-methoxy-9-(1-methylethyl)-5a,6,7,8,9,9a-hexahydrodibenzofuran, (±)-2, an intermediate of the total synthesis of (±)-linderol A 1, was acetylated and resolved by HPLC on chiral stationary phases into the respective enantiomers (−)- and (+)-3. Enantiopure (−)-2, obtained by hydrolysis of (−)-3, was treated with (−)-camphanic chloride to give the crystalline camphanate (−)-4, the absolute configuration of which was determined by X-ray crystallography. Triols (−)- and (+)-2 were converted to (−)- and (+)-1 without disrupting their stereogenic centers according to the previously reported synthesis of (±)-1. As natural (−)-linderol A 1 was derived from (−)-2, its absolute configuration was elucidated to be 5aR,6R,9R,9aS.

(E)-2-Acetyl-4-(2-diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (4b) with a characteristic conformation and (E)-2-(2-morpholinocarbo-1-methylvinyl)-7-ethoxycarbopropoxybenzo[b]furan ((E)-3b) were prepared and evaluated for their leukotriene B4 (LTB4) antagonistic activity. Compound 4b showed potent antagonistic activity against human BLT1 and BLT2 receptors. Compound (E)-3b displayed selective BLT2 receptor antagonistic activity. Both compounds were inactive to cysteinyl LT receptors.

Reaction of 2-(1-chloro-2,2-dimethylpropyl)-1-methyl-1 H -imidazole with an excess of N , N -dimethylamine at room temperature gave an abnormal adduct, trans -4,5-bis(dimethylamino)-1-methyl-2,2-dimethylpropyl-2-imidazoline, which was derived from a serial, double nucleophilic addition into the imidazole nucleus in 74% yield together with a normal S N product, 1-methyl-2-(1-dimethylamino-2,2-dimethylpropyl)-1 H -imidazole in 15% yield. The former was easily converted to 1-methyl-5-(dimethylamino)-2-(2,2-dimethylpropyl)-1 H -imidazole by only reflux in toluene in 90% yield. The scope, mechanism and limitation of these reactions are discussed.

Reaction of 2-(1-chloro-2,2-dimethylpropyl)-1-methyl-1H-irnidazoles with diethyl methylmalonate in the presence of NaH gave a normal SN product, 2-[(1,1-diethoxycarbonylethyl)-2,2-dimethylpropyl]-1-methyl-1H-imidazole (2a), and two tele-reaction products, 5-(1,1-diethoxycarbonylethyl)-1-methyl-2-(2,2-dimethylpropyl)-1H-imidazole (3a) and trans-4,5-di-(1,1-diethoxycarbonylethyl)-4,5-dihydro-1-methyl-2-(2,2-dimethylpropyl)-1H-imidazole (4a) in 5, 17 and 70% yields, respectively. The scope and mechanism of this reaction are discussed.

The effects of Ginkgo biloba leaf extract (GBE), one of the most widely used herbal dietary supplements in Japan, on the pharmacokinetics of diltiazem (DTZ), a typical probe of cytochrome P450 (CYP) 3A, were examined in rats. The simultaneous addition of GBE to small intestine and liver microsomes inhibited the formation of N-demethyl DTZ (MA), an active metabolite of DTZ produced by CYP3A, in a concentration-dependent manner, with an IC(50) of about 50 and 182 microg/ml, respectively. This inhibition appeared to be caused, at least in part, by a mechanism-based inhibition. Both the rate of formation of MA and total amount of CYP in intestinal or hepatic microsomes after a single oral pretreatment with GBE (20 mg/kg) decreased transiently. The pretreatment significantly decreased the terminal elimination rate constant and increased the mean residence time, after intravenous administration of DTZ (3 mg/kg). Furthermore, it significantly increased the area under the concentration-time curve and absolute bioavailability after oral administration of DTZ (30 mg/kg). These results indicated that the concomitant use of GBE in rats increased the bioavailability of DTZ by inhibiting both intestinal and hepatic metabolism, at least in part, via a mechanism-based inhibition for CYP3A.

1-Methyl-3-trimethylsilylparabanic acid (17) was successfully used in the final step of the total synthesis of isonaamidine A (9), isonaamidine C (11) and pyronaamidine (8), antitumor marine imidazole alkaloids.

The first total synthesis of (+/-)-Linderol A, a hexahydrodibenzofuran constituent of Lindera umbellata bark, with potent inhibitory activity on the melanin biosynthesis of cultured B-16 melanoma cells, was achieved through 19 steps of reaction in 6.6% overall yield, in which the critical step was a tandem reaction of a 3-ethoxycarbonylcoumarin derivative with dimethylsulfoxonium methylide to yield the 2-ethoxycarbonylcyclopenta[b]benzofuran-3-ol derivative.

2-Methylamino-3-(1-piperidinylmethyl)-1, 4-naphthoquinone (7) was prepared via several steps from 2-methyl-1, 4-naphthoquinone (vitamin K3, 3). The quinone (7) was photochemically oxidized to 2-methylamino-3-(1-piperidinylcarbonyl)-1, 4-naphthoquinone (8) and/or 2-alkoxycarbonyl-3-methylamino-1, 4-naphthoquinone (9), depending on the solvent used.

Alkylidenemalonates were readily dimerized in the presence of SmI2 to give 2,3-disubstituted 1,1,4,4-butanetetracarboxylates as mixtures of meso and racemic isomers in moderate to good yields. The structure of the less polar isomer of tetraethyl 2,3-diphenyl-1,1,4,4-butanetetracarboxylate was determined by X-ray crystallographic analysis to be the meso form. Characteristic 1H-NMR behavior of the meso and racemic isomers is also discussed.

2-(1-Chloro-2,2-dimethylpropyl)-1-methyl-1 H -imidazole hydrochloride ( 2a ·HCl) was treated with an excess of N,N -dimethylamine at room temperature to give an abnormal addition product, 4,5-bis( N,N -dimethylamino)-1-methyl-2-(2,2-dimethylpropyl)-2-imidazoline ( 4a ), in 74.2% yield together with a normal S N 2 product, 2-(1- N,N -dimethylamino-2,2-dimethylpropyl)-1-methyl-1 H -imidazole ( 3a ), in 15.0% yield. The former might be evolved from a serial double nucleophilic addition of the secondary amine molecules to the imidazole nucleus, which has been generally considered as an electron-excessive and stable aromatic ring.

Alkylidenemalonates were readily dimerized in the presence of SmI2 to give 2,3-disubstituted 1,1,4,4-butanetetracarboxylates as mixtures of meso and racemic isomers in moderate to good yields. The structure of the less polar isomer of tetraethyl 2,3-diphenyl-1,1,4,4-butanetetracarboxylate was determined by X-ray crystallographic analysis to be the meso form. Characteristic 1H-NMR behavior of the meso and racemic isomers is also discussed.

A newly synthesized conjugate of 7-hydroxy-3-O-phosphonocholic acid (ursodeoxycholic acid monophosphate) with 5-aminosalicylic acid (5-ASA-UDCA monophosphate) was investigated to determine its suitability for the evaluation of enteric bacteria. This compound, 5-ASA-UDCA monophosphate, was efficiently deconjugated by cholylglycine hydrolase to release 5-ASA, whereas it was completely resistant to deconjugation by pancreatic and intestinal mucosal enzymes. In everted gut sac experiments, 5-ASA-UDCA monophosphate was not actively absorbed from any part of the small intestine. In animal experiments, urinary excretions of N-acetyl-5-ASA (Ac-5ASA) were measured for 24 h following the oral administration of 20 mg of 5-ASA-UDCA monophosphate. Control rats excreted 276.3 +/- 89.0 micrograms (mean +/- S.E.) of Ac-5ASA, whereas the rats with intestinal bacterial overgrowth excreted more (1224.1 +/- 231.5 micrograms; p < 0.01). These basic studies indicate that this compound is likely to offer a simple method for the evaluation of microbial overgrowth without the use of radioisotopes or expensive, special apparatus.