Biotransformation of (+)-(1R,2S)-fenchol by the larvae of common cutworm (Spodoptera litura)

Biotransformation of (+)-(1R,2S)-fenchol by the larvae of Spodoptera litura was carried out. Substrate was converted to three new terpenoids, (+)-(1R,2S)-10-hydroxyfenchol, (+)-(1R,2R,3S)-8-hydroxyfenchol and (−)-(1S,2S,6S)-6-exo-hydroxyfenchol, and one known terpenoid, (−)-(1R,2R,3R)-9-hydroxyfenchol. These structures were established by NMR, IR, specific rotation and mass spectral studies.     

Synthesis of aza-aromatic hydroxylamine-O-sulfonates and their application to tandem nucleophilic addition-electrophilic 5-endo-trig cyclization

Hydroxylamine-O-sulfonic acid (HOSA) was used as an efficient nucleophilic amination reagent for 2-chloropyrimidines, 2-chloroquinolines, and 1-chloroisoquinoline. The newly obtained heteroaromatic hydroxylamine-O-sulfonates subjected to the reaction with acyl isothiocyanates underwent tandem nucleophilic addition-electrophilic 5-endo-trig cyclization. The mechanism of the cyclization was investigated with use of the long-range corrected hybrid density functional ωB97X-D/6-31+G^∗ and SM8 (DMF) solvation model. The structures of the heteroaromatic hydroxylamine-O-sulfonates and N-(5-methoxy-2H-[1,2,4]thiadiazolo[2,3-a]pyrimidin-2-ylidene)benzamide were confirmed by single crystal X-ray analysis. N-(2H-[1,2,4]thiadiazolo[3,2-a]isoquinolin-2-ylidene)benzamide exhibited a pronounced in vitro cytostatic activity against human tumor cell lines SISO, LCLC, A-427, DAN-G, and RT-4 (IC₅₀ in the range 1.47-2.97 μM).     

A novel synthesis of new 2-aryl-6-(arylamino)-1H-imidazo[1,2-b]pyrazole-7-carbonitrile derivatives

New 2-aryl-6-(arylamino)-1H-imidazo[1,2-b]pyrazole-7-carbonitriles are synthesized in good yields, via cyclocondensation of 5-amino-1-(2-oxo-2-arylethyl)-3-(arylamino)-1H-pyrazole-4-carbonitriles, which are prepared by the reaction of 5-amino-3-arylamino-1H-pyrazole-4-carbonitriles and α-bromoacetophenone derivatives in the presence of K₂CO₃ using acetone as the solvent.     

Highly glycosylated flavonoids from the pods of Bobgunnia madagascariensis

Methanolic extracts of the pods of Bobgunnia madagascariensis (Leguminosae) yielded four pentaglycosylated flavonoids, including the 3-O-α-l-rhamnopyranosyl(1→3)-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-β-d-glucopyranoside-7-O-α-l-rhamnopyranosides of 3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-benzopyran-4-one (kaempferol) and 3,5,7-trihydroxy-2-(3,4-dihydroxyphenyl)-4H-benzopyran-4-one (quercetin), which were characterized by a novel O-linked branched tetrasaccharide. Spectroscopic and chemical methods were used to determine the structures of the latter, which co-occurred with the corresponding β-d-galactopyranosyl isomers, and two saponins. Conformational isomerism of quercetin 3-O-α-l-rhamnopyranosyl(1→3)-α-l-rhamnopyranosyl(1→2)[α-l-rhamnopyranosyl(1→6)]-β-d-glucopyranoside-7-O-α-l-rhamnopyranoside was detected in solution by NMR, a phenomenon previously associated only with C-glycosylflavonoids.     

Synthesis of all the stereoisomers of 6-methyl-2-octadecanone, 6,14-dimethyl-2-octadecanone, and 14-methyl-2-octadecanone, the components of the female-produced sex pheromone of a moth, Lyclene dharma dharma

All of the stereoisomers of the components of the female-produced sex pheromone of a moth, Lyclene dharma dharma, were synthesized. They are (R)- and (S)-6-methyl-2-octadecanone, (6R,14R)-, (6R,14S)-, (6S,14R)-, and (6S,14S)-6,14-dimethyl-2-octadecanone, and (R)- and (S)-14-methyl-2-octadecanone. Enantiomers of citronellal and methyl (S)-3-hydroxy-2-methylpropanoate were the starting materials, and olefin cross metathesis was employed as the key reaction.     

Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

A variety of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans were easily synthesized in good yields under mild conditions by a domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylethylidene)- and 2-(1-phenylpropylidene)malononitriles. In the latter case, intermediate 7-amino-10-methyl-10-nitro-9-phenyl-6-(trifluoromethyl)-10,10a-dihydro-6H-benzo[c]chromene-8-carbonitriles were isolated as a result of a rare [1,5] sigmatropic shift of the nitro group.     

Highly efficient and selective biocatalytic acylation studies on triazolylsugars

Different acid anhydrides (of C₂ to C₇ aliphatic fatty acids and benzoic acid) have been used to study the selective acylation of primary/secondary hydroxyl groups in 2-phenyl-4-(d-threo-1′,2′,3′-trihydroxypropyl)-2H-1,2,3-triazole, 2-phenyl-4-(d-erythro-1′,2′,3′-trihydroxypropyl)-2H-1,2,3-triazole, 2-phenyl-4-(d-arabino-1′,2′,3′,4′-tetrahydroxybutyl)-2H-1,2,3-triazole and 2-phenyl-4-(d-lyxo-1′,2′,3′,4′-tetrahydroxybutyl)-2H-1,2,3-triazole in the presence of Candida antarctica lipase B in diisopropyl ether. Among the different acid anhydrides, butanoic anhydride was found to be the most efficient acylating agent (for butanoylation); for acetylation, vinyl acetate gave the best results. The reactions with both these acylating agents were highly selective and efficient yielding exclusively the monoacylated products in 95-99% yields in 1-5 h.     

2-Cyanopyridazin-3(2H)-ones: effective and chemoselective electrophilic cyanating agents

2-Cyanopyridazin-3(2H)-ones are novel, effective, selective and electrophilic cyanating agents. A variety of amino, thiol and carbon nucleophiles are chemoselectively N-, S- or C-cyanated in excellent yield using 2-cyanopyridanzin-3(2H)-ones in water or tetrahydrofuran.     

Radical mediated stereoselective synthesis of (4R,8R)-4,8-dimethyldecanal, an aggregation pheromone of Tribolium flour beetles

(4R,8R)-4,8-Dimethyldecanal, a common aggregation pheromone of Tribolium flour beetles, has been synthesized from (R)-2,3-O-isopropylideneglyceraldehyde in 11 steps and 7% overall yield. The key step in the synthesis is the highly diastereoselective chelation-controlled radical reaction of ethyl (4S,5R)-4-benzyloxy-5,6-(isopropylidenedioxy)-2-methylenehexanoate with ethyl (R)-5-iodo-3-methylpentanoate performed in the presence of 7 equiv of MgBr₂·OEt₂.     

The interaction of fluorinated 2-arylhydrazono-1,3-dicarbonyl compounds with o-phenylenediamine

2-Arylhydrazono-3-fluoroaklyl-3-oxo esters react with o-phenylenediamine under neutral conditions to form mainly o-aminoanilides, from which can be obtained 1,5-benzodiazepin-2-ones. Ethyl-2-(benzimidazol-2-yl)-2-(4-methylphenyl)hydrazonoethanoate was isolated also from the reaction of di(tri)fluoromethyl-containing 2-arylhydrazono-3-oxo esters. The reactions of o-phenylenediamine with 1,2,3-triketone 2-arylhydrazones containing alkyl substituents result in the formation of 1-(benzimidazol-2-yl)-1,2-dioxoalkane arylhydrazones, whereas phenylsubstituted analogues afford 2-phenylbenzimidazole. Nickel(II) chelates of N,N′-phenylene-bis(2-arylazo-1,3-aminovinylketones) were obtained from 1,2,3-triketone 2-arylhydrazones and o-phenylenediamine using a template method.     

Syntheses and evaluation of fluorinated benzothiazole anilines as potential tracers for β-amyloid plaques in Alzheimer's disease

[¹¹C]2-(4′-(Methylamino)phenyl)-6-hydroxybenzothiazole ([¹¹C]PIB) is a most potential PET tracer for detecting the β-amyloid plaques in Alzheimer's disease. Here the syntheses of three fluorinated PIB, namely 2-(4′-(methylamino)phenyl)-6-fluoroethoxybenzothiazole (O-FEt-PIB), 2-(4′-(methylamino)phenyl)-6-fluoro-benzothiazole (F-N-Me) and 2-(4′-(dimethylamino)phenyl)-6-fluorobenzo-thiazole (F-N,N-Me), and the radiosynthesis of one corresponding ¹⁸F-labeled PIB compound, [¹⁸F]O-FEt-PIB, as well as their in vitro/in vivo biological characters were reported. The structures of the products were confirmed by IR, ¹H NMR, EI/ESI-MS, elemental analysis and HRMS techniques. The radiolabeled product was characterized by radio-TLC and radio-HPLC and purified by semi-preparative radio-HPLC. The suitable biological characters showed these tracers were potential to be developed as probes for detecting β-amyloid plaques in Alzheimer's disease.     

PTSA catalyzed straightforward protocol for the synthesis of 2-(N-acyl)aminobenzimidazoles and 2-(N-acyl)aminobenzothiazoles in PEG

An efficient PTSA catalyzed synthesis of 2-(N-acyl)aminobenzimidazoles and 2-(N-acyl)aminobenzothiazoles has been described using S-ethylated-N-acylthioureas as substrates and polyethylene glycol as solvent.     

Synthesis, stereochemical and conformational properties of trans-2,3-dihydro-2-methyl-3-(1,2,4-triazolyl)-4H-1-benzopyran-4-one oxime ethers

A convenient synthesis and structural characterization of (Z)- and (E)-trans-2,3-dihydro-2-methyl-3-(1,2,4-triazolyl)-4H-1-benzopyran-4-one oxime ethers has been achieved. By analysis of vicinal interproton coupling constants, it is believed that trans-2,3-dihydro-2-methyl-3-(1,2,4-triazolyl)-4H-1-benzopyran-4-ones which exist predominantly in the diequatorial half-chair or sofa conformation was found to exist predominantly in the diaxial orientation upon conversion to the corresponding oxime ether derivatives.     

Cytotoxic cembranoids from the Red Sea soft coral, Sarcophyton auritum

Chemical investigation of the Red Sea soft coral Sarcophyton auritum led to the isolation and structure elucidation of two new diterpene cembranoids; 2-epi-sarcophine (2) and (1R,2E,4S,6E,8R,11R,12R)-2,6-cembradiene-4,8,11,12-tetrol (4), as well as two known diterpene cembranoids, reported for the first time from this species, namely sarcophine (1) and (+)-7α,8β-dihydroxydeepoxysarcophine (3). Structure elucidation was achieved using spectroscopic techniques, including 1D and 2D NMR and HRMS. The isolated cembranoids were found to display high cytotoxicity against HepG2 (liver cancer cell line) and MCF-7 (breast cancer cell line).     

Stereoselective radical cyclizations of N-(2-halobenzoyl)-cyclic ketene-N,X(X=O, S)-acetals

2-Alkyloxazolines and 2-alkylthiazolines react with 2-halobenzoyl chlorides to form N-(2-halobenzoyl)-cyclic ketene-N,O-acetals and N-(2-halobenzoyl)-cyclic ketene-N,S-acetals in excellent yields, respectively. These ketene acetals readily undergo stereocontrolled aryl radical cyclizations to afford the central six-membered rings of substituted-2,3,10,10α-tetrahydrooxazolo[3,2-b]isoquinolin-5-ones and their 2,3,10,10α-tetrahydrothiazolo[3,2-b]isoquinolin-5-one analogs. The tertiary N,O- and N,S-radicals formed upon aryl radical reaction at the ketene-N,X(X=O, S)-acetal double bond appear to have reasonable stability. The stereoselectivity in hydrogen abstractions by these intermediate radicals from both Bu₃SnH and (Me₃Si)₃SiH was investigated. The N,S-heterocyclic fused ring products may have potential medical value.     

Synthesis of new pyrazole-1,2,3-triazole dyads

An efficient two step synthetic methodology of new 5(4)-aryl-4(5)-[3(5)-(2-hydroxyphenyl)-1H-pyrazol-5(3)-yl]-1H-1,2,3-triazole dyads was established. The reaction of (E)-2-styryl-4H-chromen-4-ones, used as building blocks, with sodium azide, gave 4(5)-aryl-5(4)-(chromon-2-yl)-1H-1,2,3-triazoles bearing either electron-donating or electron-withdrawing substituents in their styryl moiety which upon reaction with hydrazine hydrate afforded the expected pyrazoles in moderate to very good yields.     

One-pot synthesis of 12H-benzo[b]xanthen-12-ones and naphtha[2,3-b]furans from non-naphthalene substrates

An efficient one-pot synthesis of 12H-benzo[b]xanthen-12-ones via an oxidant initiated and base promoted tandem reaction of 2-(4-(2-haloaryl)-4-hydroxybut-1-ynyl)benzaldehydes has been developed. By using similar strategy, a one-pot synthesis of naphtha[2,3-b]furans from the cascade reaction of 2-(4-hydroxy-but-1-ynyl)benzaldehydes with 2-bromoacetonitrile or α-bromocarbonyl compounds has also been achieved.     

Polyhydroxylated macrolide isolated from the endophytic fungus Pestalotiopsis mangiferae

A new polyhydroxylated macrolide, named mangiferaelactone (1) was isolated from a solid culture of the endophytic fungus Pestalotiopsis manguiferae, together with ten known compounds [(6S,1′S)-LL-P880α; (6S,1′S,2′R)-LL-P880β; (1′S,2′R)-LL-880γ; (1′R)-dehydropestalotin; (−)-5-carboxylmellein; (−)-5-methylmellein; (−)-5-hydroxylmethylmellein; arabenoic acid; 5,6-dihydro-4-methoxy-2H-pyran-2-one; and the (−)-2-hexylidene-3-methylsuccinic acid]. P. manguiferae was isolated from Hyptis dilatata, a small shrub common in the central region of Panama. The structure of compound 1 was elucidated by a combination of spectroscopic methods (IR, MS, optical rotation, 1D and 2D NMR spectroscopy). The absolute configuration of 1 was established as 4R,7R,8R,9S by application of vibrational circular dichroism (VCD). Compound 1 showed a minimum inhibitory concentration (MIC) of 1.6863 mg/mL against Listeria monocytogenes, and 0.5529 mg/mL against Bacillus cereus. No activity was observed for compound 1 against Plasmodium falciparum or Trypanosoma cruzi; likewise, no cytotoxic activity was observed against A2058 and H522-T1 cells.     

Cyclic tetrapeptides from marine bacteria associated with the seaweed Diginea sp. and the sponge Halisarca ectofibrosa

A Pseudomonas sp. was cultured which was associated with the Japanese seaweed Diginea sp. Crude extracts prepared from this bacterial culture were found to inhibit the growth of other marine bacterial strains. From this bacterial culture, two new peptides cyclo-[phenylalanyl-prolyl-leucyl-prolyl] (3) and cyclo-[isoleucyl-prolyl-leucyl-alanyl] (4) have been isolated together with two known peptides (1) and (2). The crude extract from a culture of Pseudoalteromonas sp. associated with the Thai sponge Halisarca ectofibrosa was found to inhibit the growth of Bacillus subtilis and Vibrio anguillarum. Isolation studies yielded a fraction containing two peptides that were identified as cyclo-[phenylalanyl-leucyl]₂ (5) and cyclo-[leucyl-isoleucyl]₂ (6) by means of LC-MS and 2D NMR data. Absolute stereochemistry was confirmed by the synthesis of cyclo-[l-phenylalanyl-l-leucyl]₂. Peptides (1)-(3) were also isolated from this bacterial strain. None of the individual peptides isolated in this study showed antibiotic activity.     

Tri-component reaction of 2-alkyl-4,5-dichloropyridazin-3(2H)-ones: synthesis of 5-cyano-5-(pyrimidin-2-yl)-2,7-dialkyl-5H-dipyridazino-[4,5-b:4,5-e]-4H-thiopyran-1,6-dione and 2-(4-cyanophenoxy) pyrimidine

Reaction of 2-alkyl-4,5-dichloropyridazin-3(2H)-ones with p-cyanophenol and 2-mercaptopyrimidine in the presence of base gave 2,4,5-trisubstituted-pyridazin-3(2H)-ones 4-9, 2-(4-cyanophenoxy)pyrimidine (10) and 5-cyano-5-(pyrimidin-2-yl)-2,7-dialkyl-5H-dipyridazino[4,5-b:4,5-e]-4H-thiopyran-1,6-diones 11 as a novel heterocycle.