Cytotoxic C-benzylated dihydrochalcones from Uvaria acuminata

Two new C-benzylated dihydrochalcones, isochamuvaritin (1) and acumitin (2), have been isolated from the African medicinal plant Uvaria acuminata, together with the previously reported benzylbenzoate (3), uvaretin (4), isouvaretin (5), diuvaretin (6), and uvangoletin (7). The structural elucidation of compounds 1 and 2 in spectroscopic studies is described. C-Benzylated dihydrochalcones, especially 1, 2, 4, and 6, showed considerable cytotoxicity toward human promyelocytic leukemia HL-60 cells.     

Two new special flavones from Uvaria accuminata

From the stem bark of Uvaria accuminata two new compounds, 5-methoxy-6,8,8-trimethyl-2-phenylchromene-4,7-dione (1) and a sesquiterpene-fused flavone, named acuminavone (2), were isolated together with a known flavone, desmosdomutin or dasytrichone, (5-hydroxy-6,8,8-trimethyl-2-phenylchromene-4,7-dione). The structure elucidation of compounds 1 and 2 in spectroscopic studies is described.     

Structure elucidation of cyclohexene (9Z)-octadec-9-enyl ethers isolated from the leaves of Uvaria cherrevensis (Annonaceae)

The phytochemical investigation of the leaf extract of Uvaria cherrevensis (Annonaceae) yielded three new cyclohexene (9Z)-octadec-9-enyl ethers, cherrevenols M-O (1–3), and a known fatty ester derivative (4). The structures of the isolated compounds were elucidated by spectroscopic and computer-aided molecular modelling methods. Ozone Induced Dissociation (OzID) mass spectrometry was employed to determine the C-9 position of the side chain olefinic double bonds, while ¹³C NMR spectroscopy indicated their (Z)-configurations. All isolated compounds were evaluated for their antimalarial and cytotoxic activities; all were inactive.     

Essential oil from the leaves of Xylopia langsdorfiana (Annonaceae) as a possible spasmolytic agent

Xylopia langsdorfiana A. St.-Hil. &Tul. (Annonaceae) is popularly known in the northeast of Brazil as ‘pimenteira da terra’, and an essential oil (XL-OE) was extracted from its leaves. Since Xylopia species are cited in folk medicine and diterpenes from X. langsdorfiana have spasmolytic activity, this study aimed to investigate a possible spasmolytic action of XL-OE on smooth muscle models. XL-OE (243 and 729 μg/mL) showed low pharmacologic efficacy on guinea pig trachea and rat aorta and uterus. However, in guinea pig ileum, XL-OE (27–729 μg/mL) inhibited carbachol or histamine-induced phasic contractions (1 μM) in a significant and concentration-dependent manner. In addition, XL-OE (81 μg/mL) reduced fluorescence intensity in ileal myocytes stimulated by histamine, indicating a decrease in cytosolic calcium concentration, which could explain the spasmolytic activity. Thus, XL-OE proved to be a promising natural product to be used in gastrointestinal diseases acting by modulating the cytosolic calcium concentration.     

Muricatenol, a Linear Acetogenin from Annona muricata (Annonaceae)

Annonaceous acetogenins (polyketides) are a group of extensively investigated naturalcompounds possessing antitumor, antiparasitic and pesticidal activities. Over 350acetogenins have been isolated and most of them have one to three tetrahydrofuran (THF)cores, several hydroxyls and a terminal y-lactone ring. As part of our investigation ofthe title species, we have reported four new C,, acetogeninst muricatalin',muricatalicin=, annonacin-B' and murihexol 2' and four known acetogenins4 annonac…     

Cis-bullatencin,a linear acetogenin from roots of Uvaria chamae

A novel acetogenin, cis-bullatencin, was isolated by successive chromatography of a cyclohexane extract of Uvaria chamae P. Beauv. roots. The structure was elucidated by a combination of chemical and spectroscopic methods (NMR, MS). Eight known mono-THF acetogenins--bullatencin, annotemoyin-1, solamin, uvariamicin-I, -II, -III, cis-reticulatacin and cis-uvariamicin-I--were also obtained.     

3-amino-1,2,4-benzotriazine 4-oxide: characterization of a new metabolite arising from bioreductive processing of the antitumor agent 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine).

Tirapazamine (1) is a promising antitumor agent that selectively causes DNA damage in hypoxic tumor cells, following one-electron bioreductive activation. Surprisingly, after more than 10 years of study, the products arising from bioreductive metabolism of tirapazamine have not been completely characterized. The two previously characterized metabolites are 3-amino-1,2,4-benzotriazine 1-oxide (3) and 3-amino-1,2,4-benzotriazine (5). In this work, 3-amino-1,2,4-benzotriazine 4-oxide (4) is identified for the first time as a product resulting from one-electron activation of the antitumor agent tirapazamine by the enzymes xanthine/xanthine oxidase and NADPH:cytochrome P450 oxidoreductase. As part of this work, the novel N-oxide (4) was unambiguously synthesized and characterized using NMR spectroscopy, UV-vis spectroscopy, LC/MS, and X-ray crystallography. Under conditions where the parent drug tirapazamine is enzymatically activated, the metabolite 4 is produced but readily undergoes further reduction to the benzotriazine (5). Thus, under circumstances where extensive reductive metabolism occurs, the yield of the 4-oxide (4) decreases. In contrast, the isomeric two-electron reduction product 3-amino-1,2,4-benzotriazine 1-oxide (3) does not readily undergo enzymatic reduction and, therefore, is found as a major bioreductive metabolite under all conditions. Finally, the ability of the 4-oxide metabolite (4) to participate in tirapazamine-mediated DNA damage is considered.     

2,2-Difluoro-1,3-dimethylimidazolidine (DFI). A new fluorinating agent

2,2-Difluoro-1,3-dimethylimidazolidine (DFI) is a new deoxo-fluorinating agent that is useful for the conversion of alcohols to monofluorides, and aldehydes/ketones to gemdifluorides under mild conditions.     

Magydardiendiol,diterpenoid with a new skeleton from magydaris panacifolia (umbelliferae).

Three new diterpenoids with a substituted α-cyclogeraniol skeleton have been isolated from the umbelliferae $\text{Magydaris panacifolia}$ (Vahl) Lange, for which the names of magydar-2,13-dien-11,17-diol, $\text{1}$, magydar-2,10 (20), 13-trien-17-ol, $\text{2}$, and magydar-2,10(20), 13-trien-17-yl acetate, $\text{3}$, are proposed. The structures of these substances have been deduced from spectroscopic and chemical data.     

Total synthesis of potential antitumor agent, (-)-dictyostatin

[structure: see text] The potential antitumor agent (-)-dictyostatin has been synthesized utilizing Brown crotylboration to achieve eight of the eleven chiral centers. The yield for the 26-step longest sequence is approximately 4%. The C9-C10 coupling is achieved via a stereoselective vinylzincate addition.     

Anhydrocochlioquinone A, a new antitumor compound from Bipolaris oryzae

In the search for antitumor compounds from Bipolaris oryzae, the coexistence of ophiobolins and cochlioquinones is reported for the first time. Of the compounds isolated, anhydrocochlioquinone A (7) was identified as a new antitumor agent. The structure of 7 was fully characterized by spectroscopic data, including COSY, HSQC, HMBC, and NOESY. The cytotoxicity of isolated compounds against HeLa and KB cells is also described.     

Bioactive constituents from Rollinia emarginata (Annonaceae)

From an Argentine collection of the tropical tree Rollinia emarginata (Annonaceae), vomifoliol, dehydrovomifoliol, blumenol C, loliolide, 7-epiloliolide, vanillin, dihydroactinolide, as well as other common plant constituents were obtained, and identified by their NMR and MS features compared with authentic samples. Antifeedant and toxic actions were exerted to the polyphagous moth Spodoptera frugiperda by the ethanol extract of the plant, at 250 ppm in the larval diet. Additionally, in greenhouse studies, a 200 ppm aqueous solution of the extract produced a post-emergency herbicidal effect on the annual weed common lambsquarter (Chenopodium album).     

A new nitrile oxide based synthesis of the antitumor agent geiparvarin

Geiparvarin 1 has been synthesized utilizing the 3,5-disubstituted isoxazole 8 as protected synthon for the 3(2h)furanone system, the desired α′-hydroxy-1,3-diketone precursor being eventually revealed by Mo(CO)₆ promoted reductive cleavage.     

Duryne,a new cytotoxic agent from the marine sponge Cribrochalinadura

Duryne, 1, a cytotoxic metabolite which inhibits the growth of both mouse and human tumor cell lines invitro has been isolated from the marine sponge Cribrochalinadura. Its structure has been assigned by spectral methods.     

μ-Bis(cyanotrihydroborato)-tetrakis(triphenylphosphine) dicopper(I). A new,selective, pH dependent reducing agent

The title compound selectively reduces acid chlorides to aldehydes under neutral conditions and aldehydes and ketones to alcohols in acidic media. 4-$\text{tert}$-Butylcyclohexanone is reduced to the $\text{trans}$ alcohol with a high degree of stereoselectivity (94:6).     

Bis-(p-nitrophenylethyl)phosphoromonochloridate,a new versatile phosphorylating agent

A new phosphorylating agent, bis-(p-nitrophenylethyl)phoshoromonochloridate, has been prepared and is used for 3′- and/or 5′-phosphorylations of nucleosides. The resulting bis-(p-nitrophenylethyl)phosphotriesters are versatile synthons in oligonucleotide syntheses leading finally to 3′- and/or 5′-terminated oligonucleotides in excellent yields.