Synthesis of 1-Hydroxy-10-methyl-pyrimido [1, 6-C][1, 3]oxazine and the Oxazepine Derivative,Structural Mimicry of Anti-Constrained Acyclic Thymidine

Abstract

A number of pyrimido[1, 6-c][1, 3]oxazine and -oxazepine derivatives, mimicry analogs of anti-constrained acyclic thymidine, have been prepared via treatment of lithiated 5, 6-dimethyl-2, 4-dimethoxypyrimidine with benzylchloromethyl ether or oxiran to furnish 2, 4-dimethoxy-6-(1-benzyloxyethyl)-S-methylpyrimidine (2) and 2, 4-dimethoxy-6-(1-hydroxypropyl)-5-methylpyrimidine (8), respectively. Debenzylation of 2 afforded 2, 4-dimethoxy-6-(1-hydroxyethyl)-5-methylpyrimidine (3). Chloromethylation of 3 and 8 with paraformaldehyde and gaseous hydrogen chloride produced reactive chloromethyl ether intermediates which were converted to the cyclized products 9-methyl-(1H, 2H, 4H, 7H)-pyrimido[1, 6-c][1, 3]-oxazine (5) and -oxazepine (9)-6, 8-dione, respectively. By using selenium dioxide, allylic oxidation of 5 and 9 afforded the target compounds, a racemic mixture of (±)1-hydroxy-9-methyl-(1H, 2H, 4H, 7H)-pyrimido[1, 6-c][1, 3]-oxazine (6) and -oxazepine (10)-6, 8-dione, respectively. Compounds 5, 6, 7, 9, and 10 were evaluated for activity against human immunodeficiency virus (HIV), herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV). All of these compounds were inactive.     

Labdane diterpenoids from Aframomum sceptrum: NMR study and antiparasitic activities

Two novel labdane diterpenoids, 15ξ-methoxy-labdan-8(17),11(E),13(14)-trien-15,16-olide (1) and 12(S)-hydroxy-15ξ-methoxy-labdan-8(17),13(14)-dien-15,16-olide (2) were isolated from the rhizomes of Aframomum sceptrum K. Schum (Zingiberaceae). Their structures were established on the basis of their spectroscopic data. Stigmast-4-en-6β-ol-3-one and caryophylene oxide were also obtained. In vitro trypanocidal and leishmanicidal activities of labdanes 1 and 2 were evaluated. Compound 2 exhibited activity similar to that of reference drugs against Leishmania donovani.     

Cynasibirolide A,One New Humulanolide Sesquiterpene from Cynanchum acutum subsp. sibiricum

Cynasibirolide A ( 1 ), one new humulanolide sesquiterpene, together with four known analogs, asteriscanolide ( 2 ), (1S,8S)-8-hydroxyhumula-2Z,6E,9E-trien-1,12-olide ( 3 ), (1S,7R)-8-oxohumula-2Z,9E-dien-1,12-olide ( 4 ), and (+)-6,7,9,10-tetrahydroasteriscunolide ( 5 ) were isolated from the roots and rhizomes of Cynanchum acutum subsp. sibiricum. Their structures and configurations were elucidated by spectroscopic methods, including 2D-NMR techniques, and the structure of 1 was confirmed by single-crystal X-ray diffraction. All compounds were evaluated for their anti-complementary activity in vitro, and compound 3 exhibited anti-complement effect with CH₅₀ value of 0.45 mM.     

Lysis of Radio-resistant Bacteria by Enzyme of Achromobacter lunatus

An unknown polyacetylene was isolated from the subterranean stems of Solidago altissima L. in which the two poly acetylenes, dehydromatricaria ester (I) and methyl 10-[(Z)-2-methyl- 2-butenoyloxy]-(2Z,8Z)-2,8-decadiene-4,6-diynoate (II) had already been found, and its structure was identified as (4Z)-2,4-decadiene-6,8-diyn-4-olide (dehydromatricaria lactone) (III). The lactone (III), as well as I, strongly inhibited the growth of the seedlings of barnyard millet (Panicum crus-galli L. var. frumentaceum Trin.).

The seasonal variations in the polyacetylene contents of the subterranean stems were closely investigated, with the results that III occurred only in the fall of the year while I and II hardly varied throughout the year. II was a major polyacetylene component and the content was 0.9~1.0 µmol/g fresh wt.     

Synthesis and Reactions of Some Glycosylamine Derivatives of 6-Azauracil Nucleosides

Abstract

Reaction of the silylated 6-azauracil (2) with 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-D-glucose (3) gave 1-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-ß-D-glucopyranosyl)-6-azauracil (4), which gave the free nucleoside 5 on deblocking. Acetalation of 5 gave the monoacetal 6 which was oxidized into the ketone 7. Reduction of 7 gave the allo-nucleoside 9 which on hydrolysis afforded the free nucleoside 10. Alternatively, compound 10 was obtained from mesylation of 6 to give 8 followed by subsequent acetolysis and hydrolysis.     

Sesquiterpene lactones,flavonoids and anthraquinones from Asphodeline globifera and Asphodeline Damascena

The known compounds chrysoeriol, apigenin, luteolin, acacetin, scutellarein, 6-methoxyluteolin, apigenin 7-glucoside, luteolin 7-glucoside, esculetin, chrysophanol, asphodeline, mircocarpin, sitosterol, 1-β-acetoxyeudesman-4(15),7(11)dien-2α,12-olide and 1-β-acetoxy-8β-hydroxyeudesman-4(15),7(11)-dien-8α,12-olide were isolated from Asphodeline globifera and A. damascena. A new sesquiterpene lactone 1-β-acetoxy-8β-ethoxyeudesman-4(15),7(11)dien-8α, 12-olide was also characterized. These are the first reports of sesquiterpene lactones in Asphodeline and in the Liliaceae.     

Hydroxylation of (+)-menthol by Macrophomina phaseolina

Abstract

Biotransformation of (+)-menthol with Macrophomina phaseolina led to hydroxylations at C-1, C-2, C-6, C-7, C-8 and C-9, with the C-8 position being preferentially oxidized. The resulting metabolites were identified as 8-hydroxymenthol (2), 6R-hydroxymenthol (3), 1R-hydroxymenthol (4), 9-hydroxymenthol (5), 2R,8-dihydroxymenthol (6), 8S,9-dihydroxymenthol (7), 6R,8-dihydroxymenthol (8), 1R,8-dihydroxymenthol (9) and 7,8-dihydroxymenthol (10). Metabolites 6–10 are described here for the first time. Their structures were characterized by spectroscopic analysis.     

Constituents of Limonia acidissima inhibit LPS-induced nitric oxide production in BV-2 microglia

The ethyl acetate (EtOAc) soluble fraction of the 85% ethanol (EtOH) extract of the dried bark of Limonia acidissima potently inhibited nitric oxide (NO) production in lipopolysaccharide (LPS) activated BV-2 cells, a microglial cell line. Bioassay-guided column chromatography separation afforded a new stereoisomer of neolignan, (7’E)-(7R,8S)-4-hydroxy-3,5’-dimethoxy-4’,7-epoxy-8,3’-neolig-7’-en-9,9’-diyil diacetate (1), together with two known lignans, (+)-yangambin (2) and (+)-syringaresinol (3), three known triterpenoids, hederatriol (4), basic acid methyl ester (5), and 3β-hydroxyolean-12-en-11-one (6), and four known fatty acid derivatives, cascarillic acid (7), (+)-α-dimorphecolic acid (8), 8(R)-hydroxylinoleic acid (9), and (6Z,9Z,12Z)-pentadecatrienoic acid (10). The structure of the new compound 1 was elucidated by detailed analysis of spectroscopic data and circular dichroism (CD) spectroscopy. Compounds 1, 3-6, and 8-10 isolated from L. acidissima significantly reduced NO production in LPS-stimulated BV-2 microglia cells.     

Two new sesquiterpenes from Ligularia dictyoneura

The detailed investigation of the whole plant of Ligularia dictyoneura was performed during a search for unique chemical skeletons. One novel noreremophilane-type sesquiterpene, (4S, 5R, 8R, 10S)-1-nor-10-hydroxy-8-methoxyeremophil-7(11)-en-12,8-olide (1) and one new highly oxygenated eremophilane, 1β-angeloyloxy-6α, 10β-dihydroxyeremophil-7(11), 8-dien-12, 8-olide (2), were obtained. Their structures, including the absolute configuration, were elucidated by spectroscopic data and CD analysis.     

Guaianolides and elemanolides from Vernonia anthelmintica

Two new guaianolides, (1R,4R,5S,6R,7R,8S)-8,15-dihydroxyguaia-10(14),11(13)-dien-12,6-olide (1) and (1R,4R,5S,6R,7R,8S,11S)-8,15-dihydroxyguaia-10(14)-en-6,12-olide (2), and two known elemanolides, (4S,5R,6R,7R,8S,10R,11S)-11,13-dihydrovernolepin (3) and (5R,6R,7R,8S,10R,11S)-melitensin (4) were isolated from the aerial parts of Vernonia anthelmintica Willd. The structures of these compounds were determined on the basis of IR, UV, MS, 1D-NMR and 2D-NMR, and their absolute configurations were deduced using the CD exciton chirality method and single-crystal X-ray diffraction. The possible biosynthetic relationships of compounds 1–4 are postulated. Compounds 1–4 were evaluated for their cytotoxicity against HL-60 and SMMC-7721 cell lines.     

Synthesis and Antiviral Activity of Carbocyclic Nucleosides Incorporating a Modified Cyclopentane Ring. Part 3: Adenosine and Uridine Analogues

Abstract

Six new carbocyclic nucleosides were prepared by mounting a purine (compounds 4–6), 8-azapurine (7 and 8) or undine (9) base on the ammo group of (1S,3R)-3-amino-2,2,3-trimethylcyclopentylmethanol (10). At subtoxic concentrations, compounds 5-9 showed at best marginal antiviral activity.     

Semisynthesis and cytotoxic activities of andrographolide analogues

Andrographolide 1, a diterpenoid lactone of the plant Andrographis paniculata, known to possess antitumour activity in in vitro and in vivo breast cancer models was subjected to semisynthesis leading to the preparation of a number of novel compounds. These compounds exhibited in vitro antitumour activity with moderate to excellent growth inhibition against MCF-7 (breast) and HCT-116 (colon) cancer cells. Compounds 3,19-(2-chlorobenzylidene)andrographolide(5), 3,19-(3-chlorobenzylidene)andrographolide(6), 3,19-(3-fluorobenzylidene)andrographolide(7), 3,19-(4-fluorobenzylidene)andrographolide(8), 3,19-(2-fluorobenzylidene)andrographolide(10), 3,19-(2-chloro-5-nitrobenzylidene)andrographolide (21), 3,19-(4-chlorobenzylidene)andrographolide(30) and 3,19-(2-chloro-4-fluorobenzylidene) andrographolide(31) were also screened against 60 NCI (National Cancer Institute, USA) human tumour cell lines derived from nine cancer cell types.     

The germacranolides of Viguiera buddleiaeformis structures of budlein-A and -B

The structure of budlein-A, the main sesquiterpene lactone of Viguiera buddleiaeformis was established as the 8 angeloyl ester of 1 keto, 8-β, 14-dihydroxy germacra-2,4,11 (13)-trien-3, (10 β) oxido-6 α, 12-olide. Its structure and stereochemistry was determined by chemical and spectroscopic means. Budlein-B, found in the same plant as a minor constituent, is 8 α, 15-dihydroxygermacra-1 (10), 4, 11 (13)-trien-6 α, 12-olide.     

New Steroidal Glycosides from Rhizomes of Clintonia udensis

A total of 10 steroidal glycosides, together with three new spirostanol glycosides (6–8), a new furostanol glycoside (9), and a new cholestane glycoside (10), were isolated from the rhizomes of Clintonia udensis (Liliaceae). The structures of the new compounds were determined on the basis of extensive spectroscopic analyses, including 2-D nuclear magnetic resonance (NMR) data, and of hydrolytic cleavage followed by chromatographic or spectroscopic analyses. The isolated glycosides were evaluated for their cytotoxic activity against HL-60 leukemia cells. Spirostanol glycosides 1 and 2, and furostanol glycoside 4 showed cytotoxic activity with IC₅₀ values of 3.2±0.02, 2.2±0.12, and 2.2±0.06 μg/ml, respectively. Neither the spirostanol and furostanol saponins with a hydroxy group at C-1 (6 and 9) and C-12 (7 and 8) nor cholestane glycosides (5 and 10) exhibited apparent cytotoxic activity at a sample concentration of 10 μg/ml.     

Microbial transformation of neoandrographolide by Mucor spinosus (AS 3.2450)

Microbial transformation of neoandrographolide (1), was performed by Mucor spinosus (AS 3.2450). Ten metabolites were obtained and identified as 14-deoxyandrographolide (2), 17,19-dihydroxy-8,13-ent-labdadien-16,15-olide (3), 3,14-dideoxyandrographolide (4), 7β-hydroxy-3,14-dideoxyandrographolide (5), 17,19-dihydroxy-7,13-ent-labdadien-16,15-olide (6), 8(17),13-ent-labdadien-16,15-olid-19-oic acid (7), 8α,17β-epoxy-3,14-dideoxyandrographolide (8), 8β,17,19-trihydroxy-ent-labd-13-en-16, 15-olide (9), phlogantholide-A (10), 19-[(β-d-glucopyranosyl)oxy]-19-oxo-ent-labda-8(17),13-dien-16,15-olide (11) by spectroscopic and chemical means. Among them, products 3, 5, 6, 8 and 9 were characterized as new compounds. The inhibitory effects of compounds 1–11 on nitric oxide production in lipopolysaccharide-activated macrophages were evaluated and their preliminary structure–activity relationships (SAR) were discussed.     

A New Ribityllumazine Derivative

Lipase-catalyzed enantioselective lactonization of racemic methyl 6-phenyl-4-hydroxy-5-hexynoate worked well to afford (R)-6-phenyl-5-hexyn-4-olide (42% yield, 81% e.e.). The e.e. of the product was enhanced to 97% by the repetition of enzymatic reaction. From this lactone, (4R,5R)-isomer of 5-hydroxy-6-phenyl-4-hexanolide, a lateral root inducing substance from Erwinia quercina was synthesized via a selective epoxidation of the intermediate and subsequent hydrogenolysis as the keystep.     

New derivatives from the aerial parts of Boerhaavia diffusa L. (Nyctaginaceae)

Boerhaavia diffusa L. is used in the traditional medicine of several Asian countries. The isolation and identification of five new compounds, together with 11 known compounds, from the ethyl acetate extract of the aerial part of B. diffusa grown Vietnam is reported. The structure of the new compounds was established by 1D and 2D NMR spectroscopy, and high resolution ESI-MS analysis. New compounds are two rotenoids: 9,11-dihydroxy-6,10-dimethoxy[1]benzopyrano[3,4-b][1]benzopyran-12(6H)-one (boeravinone P, 3) and 3-[2-(β-d-glucopyranosyloxy)-3-hydroxyphenyl]-5-hydroxy-2-hydroxymethyl-7-methoxy-6-methyl-4H-1-benzopyran-4-one (boeravinone Q, 9), an atropisomeric mixture of two rotenoid glycosides (3′,5-dihydroxy-2-hydroxymethyl-7-methoxy-6-methylisoflavone 2′-O-β-d-glucopyranoside, 11), a sesquiterpene lactone (4,10-dihydroxy-8-methoxyguai-7(11)-en-8,12-olide, 5) and a new phenylpropanoid glycoside (boerhaavic acid, 15).     

Antifouling Activity of Bromotyrosine-Derived Sponge Metabolites and Synthetic Analogues

Eighteen brominated sponge-derived metabolites and synthetic analogues were analyzed for antilarval settlement of Balanus improvisus. Only compounds exhibiting oxime substituents including bastadin-3 (4), −4 (1), −9 (2), and −16 (3), hemibastadin-1 (6), aplysamine-2 (5), and psammaplin A (10) turned out to inhibit larval settling at 1 to 10 μM. Analogues of hemibastadin-1 (6) were synthesized and tested for structure activity studies. Debromohemibastadin-1 (8) inhibited settling of B. improvisus, albeit at lower concentrations than hemibastadin-1 (6). Both 6 and 8 also induced cyprid mortality. 5,5′-dibromohemibastadin-1 (7) proved to be nontoxic, but settlement inhibition was observed at 10 μM. Tyrosinyltyramine (9), lacking the oxime function, was not antifouling active and was non-toxic at 100 μM. Hemibastadin-1 (6) and the synthetic products showed no general toxicity when tested against brine shrimp larvae. In contrast to the lipophilic psammaplin A (10), the hydrophilic sulfated psammaplin A derivative (11) showed no antifouling activity even though it contains an oxime group. We therefore hypothesize that the compound needs to cross membranes (probably by diffusion) and that the target for psammaplin A lies intracellularly.     

Novel Taxa-4(20),12-diene and 2(3→20)Abeotaxane from Needles of Taxus canadensis

A novel 6/8/6-membered taxane with a rare C-12(13)-double bond and rare 2(3→20)abeotaxane were isolated from the needles of Taxus canadensis. Their structures were characterized as 7β,9α,10β-triacetoxytaxa-4(20),12-diene-2α,5α,11β-triol (1) and 2α,7β,10β-triacetoxy-5α-hydroxy-2(3→20)abeotaxa-4(20),11-diene-9,13-dione (2) on the basis of 1D and 2D spectroscopic data. 1 is the first example of a natural taxane without substitution at both C-13 and C-14.     

Screening of free radical scavengers from Erigeron breviscapus using on-line HPLC-ABTS/DPPH based assay and mass spectrometer detection

Erigeron breviscapus is a well-known traditional Chinese herbal medicine. In this study, on-line HPLC-ABTS/DPPH assay coupled with MS detection were applied to screen and identify the free radical scavengers in 70% methanol extracts of E. breviscapus. Using on-line HPLC-ABTS-MS and HPLC-DPPH-MS assay, 13 radical scavengers (including 4-O-caffeoylquinic acid (4-CQA) (1), 9-caffeoyl-2,7-anhydro-2-octulosonic acid (9-COA) (2), 3-caffeoyl-2,7-anhydro-3-deoxy-2-octulopyranosonic acid (3-CDOA) (3), erigeside I (4), quercetin-3-O-glucuronide (5), eriodictyol-7-O-glucuronide (6), scutellarin (7), 1,4-di-O-caffeoylquinic acid (1,4-di-CQA) (8), 3,5-di-CQA (9), 1-malonyl-3,5-di-CQA (10), erigoster B (11), 4,5-di-CQA (12) and 4,9-di-CDOA (13)) and 9 radical scavengers (including 1, 4, 7, 8, 9, 10, 11, 12 and 13) were discovered, respectively. Furthermore, the anti-oxidative activities of 4 compounds, including 7, 9, 11 and 12 were evaluated. Reverse anti-oxidative activity order of scutellarin and 3,5-di-CQA was observed in on-line HPLC-ABTS assay and on-line HPLC-DPPH assay. To validate their anti-oxidative activities, the off-line ABTS and DPPH assays were performed. Given sufficient reaction time, 3,5-di-CQA showed higher activity than scutellarin, which was consistent with the order obtained in on-line HPLC-ABTS assay. These results revealed that on-line HPLC-ABTS assay is a more sensitive method for screening and determining free radical scavengers, especially more suitable for those compounds with slower reaction kinetics.