Spektroskopische untersuchungen von neuen ungewöhnlich oxidationsstabilen kationenradikalen quartärer pyridiniumverbindungen

The novel compounds 1,1″-dimethyl[4,2′;4′,4″]terpyridiniumdiperchlorate (6), 1,1′,1″-trimethyl[4,2′;4′,4″]terpyridiniumtriperchlorate (7) and 1,1″,1‴-trimethyl[4,2′;4′,4″;6′,4‴]quaterpyridinium-triperchlorate (8) were synthesized. (6) and (8) give, upon reduction with Zn, stable radical cations which were investigated by [¹H]NMR-, vis- and ESR-spectroscopy and cyclovoltammogrammes.     

Biphenyl quinolizidine lactone alkaloids from “sinicuichi” (Heimia salicifolia)

Six new biphenyl quinolizidine lactone alkaloids: 14α-hydroxydecodine (1), 14β-hydroxydecodine (2), 4″-O-demethylheimidine (3), 4″-O-demethyl-9β-hydroxyvertine (4), 4″-O-demethylvertine N-oxide (5), and 4″-O-demethyl-9β-hydroxyvertine N-oxide (6) were isolated from so-called “sinicuichi” (origin: Heimia salicifolia) together with 18 known alkaloids. Their structures were determined by spectroscopic analyses and chemical conversions.     

Highly oxidized ergosterols and isariotin analogs from an entomopathogenic fungus,Gibellula formosana,cultivated in the presence of epigenetic modifying agents

The concomitant addition of a histone deacetylase inhibitor, suberoyl bis-hydroxamic acid, and a DNA methyltransferase inhibitor, RG-108, to the culture medium of Gibellula formosana, an entomopathogenic fungus, induced a significant increase in diversity of secondary metabolites. From the culture media were isolated two new highly oxidized ergosterols, formosterols A (1) and B (2), and five new isariotin analogs, 12′-O-acetylisariotin A (4), 1-epi-isariotin A (5), and isariotins K–M (6–8), together with 22,23-epoxy-3,12,14,16-tetrahydroxyergosta-5,7-dien-11-one (named formosterol C) (3), isariotins A (9), C (10), and E (11), TK-57-164A (12), and beauvericin (13). The NMR spectra, X-ray single crystallographic diffraction, and chemical transformations revealed the structures of the two new formosterols and five new isariotins. The stereochemistry of formosterol C (3) was deduced from its spectroscopic data. The side chains of formosterols A–C (1–3) contained cis-22,23-epoxide, which is rarely present in naturally occurring sterols and triterpenes.     

Determination of the configurations of tertiary alcoholic centers in branched-chain carbohydrate derivatives : PMR spectroscopy with a lanthanide shift-reagent

Examination of the PMR spectral changes (expressed as shift gradients of individual protons) wrought by graduated addition of the paramagnetic lanthanide complex tris [1,1,1,2,2,3,3-heptafluoro- 7,7-dimethyloctane-4,6-dionato]europium(III) [Eu(fod)₃] permitted assignment of the configuration at tertiary alcoholic centers of certain sugar derivatives. The configurations of the tertiary position of 3- C-(1,3-dithian-2-yl)-1,2:5,6-di-O-isopropylidene-α-d-allofuranose (1), lethyl of 4,6-O-benzylidene-2- deoxy-3-C-(dithian-2-yl)-α-d-ribo-hexopyranoside (2) and the corresponding 3-C-butyl compound (2a), and methyl 2-C-(1,3-dithian-2-yl)-3,4-O-isopropylidene-δ-d-ribopyranoside (3) were assigned by comparison with reference spectra. The proton shift-gradients for 5-C-benzoyloxymethyl-2,3-O- cyclohexylidene-1-O-p-tolylsulfonyl-1(R),2(S),3(S),5(R)-cyclohexanetetrol (4), taken in conjunction with the spin-spin coupling values, permit direct assignment of relative stereochemistry in the latter compound.     

Antimicrobial and antispasmodic tetrahydroanthracenes from Cassia singueana

Four tetrahydroanthracene derivatives with antimicrobial and antispasmodic activities have been isolated from Cassia singueana. The evidence described in the following indicates them to be torosachrysone (1), germichrysone (4), and two new dimeric tetrahydroanthracenes, singueanol-I (7) or 6,6′-dimethoxy-3, 3′,8,8′,9,9′-hexahydroxy-3,3′,7,7′-tetramethyl-3,3′,4,4′-tetrahydro(10,10′-bianthracen)-1,1′(2H,2′H)-dione, and singueanol-II (8) or 6,6′-dimethoxy-3,3′,8,8′,9,9′-hexahydroxy-3,3′,7,7′-tetramethyl-3,3′,4,4′-tetrahydro(5,10′-bianthracen)- 1′(2H,2′H)-dione.     

New acetylated flavone C-glycosides from Iris lactea

Chemical investigation of the aerial parts of Iris lactea afforded three new flavone C-glycosides including 4?-O-acetyl-embinin (1), 2?,4?-O-diacetyl-embinin (2) and 6″,4?-O-diacetyl-embinin (3) along with the known analogue embinin (4). Their structures were elucidated by 1D and 2D NMR spectroscopic analysis as well as by HRESIMS data. The sugars were characterized following acid hydrolysis of the respective glycosides and TLC analysis compared to known standards. Duplicated signals can be observed in the NMR spectra, indicating the presence of rotamers caused by rotational hindrance around the glycosyl-flavone CC linkage. All isolated compounds were tested for their antimicrobial and cytotoxic activities but found to be inactive.     

Two new prenylated isoflavones from Maclura cochinchinensis collected in Hoa Binh province Vietnam

Two new prenylisoflavones, 3′,4′,5-trihydroxy-8-prenyl-dihydrofuran[2″,3″:7,6]isoflavone (1) and 4′,5-dihydroxy-8-prenyl-dihydrofuran[2″,3″:7,6]isoflavone (2), along with five known prenylisoflavones (3–7), benzylalcohol-4-O-β-d-glucoside (8) and two cinnamic acid esters (9, 10) were isolated from the leaves of Maclura cochinchinensis (Cudrania cochinchinensis). Their structures were elucidated by analysis of NMR (¹H-, ¹³C-NMR, HSQC, HMBC), MS spectra and comparison with the published data. Compounds 4–10 were the first time isolated from this species. Prenylisoflavones 1–4 and 6–7 were evaluated for their in vitro cytotoxic activity on KB and HepG2 cancer cell lines. Compound 4 showed cytotoxic activity against both cancer cell lines with IC₅₀ values of 26.99 and 19.95 μM, respectively. The other compounds were considered as inactive.     

New 1,3-amino alcohols derived from ketopinic acid and their application in catalytic enantioselective reduction of prochiral ketones

New 1,3-amino alcohols, (1S,2S)- and (1S,2R)-1-hydroxylmethyl-2-amino-7,7-dimethyl bicyclo[2,2,1]heptane (endo-4 and exo-4), were prepared from ketopinic acid via oximation and reduction. The enantioselective borane reduction of prochiral ketones catalyzed by the borane complex of exo-4 was examined.     

Phloroglucinol derivatives and a chromone glucoside from the leaves of Myrtus communis

Seven new phloroglucinol derivatives, myrtucommunins A–D (1–4), 6-methylisomyrtucommulone B (5), 4-methylmyrtucommulone B (6), and 2-isobutyryl-4-methylphloroglucinol 1-O-β-d-glucopyranoside (7), and one new chromone derivative, undulatoside A 6′-O-gallate (8), were isolated from the leaves of Myrtus communis (Myrtaceae). Myrtucommunins A–D (1–4) were conjugates of polymethylated acylphloroglucinol and flavonol rhamnoside. The absolute configurations of the rhamnosyl moieties for 1–4 were confirmed to be l in each case by HPLC analyses, while those of the aglycones were assigned by comparisons of the experimental and TDDFT calculated ECD spectra. 6-Methylisomyrtucommulone B (5) and 4-methylmyrtucommulone B (6) were assigned as 6/6/6 tricyclic acylphloroglucinol derivatives with a racemic nature. Antimicrobial activities of 1–8 and related known compounds were evaluated.     

Synthesis of linear and cyclic compounds containing the 3,4-bis(furazan-3-yl)furoxan fragment

Some chemical transformations of 3,4-bis(4-aminofurazan-3-yl)furoxan (1) and 3,4-bis-(4-nitrofurazan-3-yl)furoxan (2) were considered. Compounds 1 and 2 are valuable synthons for the preparation of linear and cyclic compounds containing the 3,4-bis(furazan-3-yl)furoxan fragment. The reaction of compound 2 with a series of N- and O-nucleophiles afforded novel heterocyclic systems: 7-R-7H-difurazano[3,4-b:3′,4′-f]furoxano[3″,4″-d]azepine and difurazano[3,4-b:3′,4′-f]furoxano[3″,4″-d]oxepin.     

Secondary metabolites of the lichen-associated fungus Apiospora montagnei

The endolichenic fungus Apiospora montagnei isolated from the lichen Cladonia sp. was cultured on solid rice medium, yielding the new diterpenoid libertellenone L (1), the new pyridine alkaloid, 23-O-acetyl-N-hydroxyapiosporamide (2) and the new xanthone derivative 8-hydroxy-3-hydroxymethyl-9-oxo-9H-xanthene-1-carboxylic acid methyl ether (3) together with 19 known compounds (4–22). The structures of the new compounds were elucidated by 1D and 2D NMR spectra as well as by HRESIMS data. The absolute configuration of the new 6,7-seco-libertellenone derivative 1 was determined by single-crystal X-ray diffraction. Four additional known compounds 23–26 were isolated when NaCl or NH₄Cl were added to solid rice medium. Compounds 7–9, 18 and 26 exhibited significant cytotoxicity against the L5178 murine lymphoma cell line with IC₅₀ values of 2.6, 0.2, 2.1, 2.7 and 1.7 μM, respectively.     

Aplyronines D–H from the sea hare Aplysia kurodai: isolation,structures, and cytotoxicity

Five cytotoxic macrolides, aplyronines D–H (4–8), were isolated from the Japanese sea hare Aplysia kurodai. They are new congeners of the antitumor compound aplyronine A (1), which was previously isolated from the same organism. Their structures were determined by spectroscopic analysis (NMR and MS). The cytotoxicity of these new compounds was evaluated in comparison with that of aplyronines A–C (1–3), suggesting the importance of the 7-O-seryl ester group for mediating the potent cytotoxicity of aplyronines.     

Four new constituents from Taraxacum mongolicum

Two new flavone glycosides,isoetin-7-O-β-D-glucopyranosyl-2′-O-α-L-arabinopyranoside (1) and isoetin-7-O-β-D-glucopyr- anosyl-2′-O-α-D-glucopyranoside (2),a new lignan,mongolicumin A (3),and a new guaianolide,mongolicumin B (4) were isolated from the aerial part of Taraxacum mongolicum.Their structures were elucidated mainly by spectral analyses.     

Chemical Modification of Kanamycin A. II. Nucleophilic Displacement Reactions of Kanamycin-A-4″-sulfonates

Abstract

Reactions of 2′,3′,4′,2″,6″-penta-O-acetyl-tetra-N-tert-butyloxycarbonyl-kanamycin-A-4″-brosylate (4b) or-4″-triflate (4c) with acetate, thiolacetate, azide, and fluoride, respectively, result in the formation of the corresponding derivatives of 4″-epi-kanamycin A (5a-d). While 4b invariably forms an elimination byproduct (9), the only side—reaction of 4c consists in a neighboring group attack with formation of a 3″-epi-4″-cyclic urethane (7). Removal of the protecting groups yields 4″-epi-(6a), 4″-thio-4″-epi-(6b), 4″-deoxy-4″-fluoro-4″-epi-(6d), 4″-azido-4″-deoxy-4″-epi-(6c), and after hydrogenation of the latter, 4″-amino-4″-deoxy-4″-epi-kanamycin A (6f).

Methyl 2,6-di-O-acetyl-3-amino-3-N-tert-butyloxycarbonyl-3-deoxy-4-O-triflyl-β-D-glucopyranoside (1b) served as a model to anticipate preparation, handling, and reactivity of 4c.     

Synthesis,structure, and conformation of terphenylene-derived azacalix[4]aromatics

Several novel azacalix[4]aromatics constituting terphenylene units have been synthesized via sequential nucleophilic aromatic substitution reactions of 5′-t-butyl-(1,1′:3′,1″-terphenyl)-3,3″-diamine 9 and 5′-t-butyl-(1,1′:3′,1″-terphenyl)– 4,4″-diamine 11 with 1,5-difluoro-2,4-dinitrobenzene and cyanuric chloride, respectively. The bridging –NH– functions of the tetra-nitro substituted azacalix[2]arene[2]terphenylenes 1 and 2 have been transformed to the corresponding –N(CH₃)– bridged azacalix[2]arene[2]terphenylenes 3 and 4 via N-alkylation. Single crystal X-ray analysis revealed that the terphenyl-3,3″-diamine derived azacalix[2]terphenylene[2]triazine 5 adopts a distorted chair conformation in the solid state, and the terphenyl-4,4″-diamine derived azacalix[2]terphenylene[2]triazine 6 was found to adopt a 1,3-alternate conformation.     

Structural and crystal chemistry analysis of (4<Emphasis Type="Italic">E</Emphasis>)- and (4<Emphasis Type="Italic">Z</Emphasis>)-6,6′,7,7′-tetrahydro-5H,5′H-4,4′-<Emphasis Type="Italic">bis</Emphasis>-1-benzothiophenes

(4E)-6,6′,7,7′-tetrahydro-5H,5′H-4,4′-bis-1-benzothiophene and (4Z)-6,6′,7,7′-tetrahydro-5H,5′H-4,4′-bis-1-benzothiophene are studied by means of X-ray diffraction. The intermolecular interaction energy is calculated and the structural subclass of each compound is derived. These compounds have been found to have similar full crystal energies and packing efficiencies. The observed pseudosymmetry effects are described.     

Five novel norcembranoids from Sinularia leptoclados and S. parva

Three new norcembrane-based diterpenoids, leptocladolides A (1), B (4) and C (5), along with five known metabolites 6-10, have been isolated from the dichloromethane extract of a Taiwanese soft coral Sinularia leptoclados. Furthermore, a chemical investigation on the dichloromethane extract of S. parva has resulted in the isolation of two new related isomers, 1-epi-leptocladolide A (2) and 7E-leptocladolide A (3), in addition to 1 and 7. The structures of new metabolites 1-5 were elucidated on the basis of extensive spectroscopic analyses and their relative stereochemistries were determined by NOESY experiments. The new metabolites 1 and 3 have been shown to exhibit significant cytotoxic activity against KB and Hepa59T/VGH cancer cell lines.     

Reaction of thieno[2,3-b]pyridines with sodium hypochlorite: An unusual and stereoselective one-pot approach to dimeric pyrrolo[2′,3′:4,5]thieno[2,3-b]pyridines

The oxidation of 3-aminothieno[2,3-b]pyridine-2-carboxamides with commercially available bleach leads to the formation of dimeric pyrrolo[2′,3′:4,5]thieno[2,3-b]pyridines (7a,14a-diamino-7,14-bis(aryl)-7,7a,14,14a-tetrahydro-6H,13H-pyrido[3″″,2″″:4?,5?]thieno[2?,3?:4″,5″]pyrrolo-[3″,4″:3′,4′]pyrrolo[2′,3′:4,5]thieno[2,3-b]pyridine-6,13-diones) in moderate yields (37–52%).     

In vitro anthelmintic and cytotoxic activities of extracts from the stem barks of Berlinia confusa (C. Hoyle) and identification of its active constituents

Phytochemical investigation of EtOAc extract from the stem bark of Berlinia confusa yielded a new and two known polysaturated monoacylglycerides characterised as 1-O-docosanoyl-sn-glyceride (3), 1-O-(13-methyltetradecanoyl)-sn-glycerol (4) and 1-O-pentadecacanoyl-sn-glycerol (5); along with the known compounds betulinic acid (1) and sitosteryl-β-d-glucoside (2). The structures of these compounds were elucidated using analytical methods, including 1D and 2D-NMR together with MS spectroscopy. The extracts and isolated compounds demonstrated concentration-dependent anthelmintic activities against Fusciola gigantica (liver flukes) and Taenia solium (tapeworm) at 10–100 mg/ml. The extracts and isolated compounds were evaluated for cytotoxicity against a small panel of three human tumour cell lines.     

3-Oxyanthranilic acid derivatives from Actinomadura sp. BCC27169

Eight new compounds including 9′-[2-amino-3-(4″-O-methyl-α-rhamnopyranosyloxy) phenyl]nonanoic acid (1), 9′-[2-amino-3-(4″-O-methyl-α-ribopyranosyloxy)phenyl] nonanoic acid (2), 11′-[2-amino-3-(4″-O-methyl-α-rhamnopyranosyloxy)phenyl]undecanoic acid (3), 11′-[2-amino-3-(4″-O-methyl-α-ribopyranosyloxy)phenyl]undecanoic acid (4), 8-(4′-O-methyl-α-rhamnopyranosyloxy)-3,4-dihydroquinolin-2(1H)-one (5), 8-(4′-O-methyl-α-ribopyranosyloxy)-3,4-dihydroquinolin-2(1H)-one (6), 8-(4′-O-methyl-α-rhamnopyranosyloxy)-2-methyquinoline (7), and 8-(4′-O-methyl-α-ribopyranosyloxy)-2-methylquinoline (8) were isolated from Actinomadura sp. BCC27169. The chemical structures of these compounds were determined based on NMR and high-resolution mass spectroscopy. The absolute configurations of these monosaccharides were revealed by the hydrolysis of compounds 7 and 8. Compounds 3 and 8 exhibited antitubercular activity at MIC 50 μg/mL. Only compound 3 showed cytotoxicity against KB cell at IC₅₀ 18.63 μg/mL, while other isolated compounds were inactive at tested maximum concentration (50 μg/mL).