Cytotoxic sesterterpenes, 6-epi-ophiobolin G and 6-epi-ophiobolin N, from marine derived fungus Emericella variecolor GF10

Two new sesterterpenes, 6-epi-ophiobolin G (1) and 6-epi-ophiobolin N (3), and six known ophiobolins were isolated from the extracts of the fungus, Emericella variecolor GF10, which was separated from marine sediment. The planar structures of the new compounds were deduced from analysis of the 2D NMR spectra, and the stereochemistry was determined by extensive examination of the NOESY spectrum. Additionally, the configuration of the C-6 proton in ophiobolin G (2) was revised from α to β, and the unsolved stereochemistry of ophiobolin H (4) was determined by its physicochemical evidence and the chemical correlation with ophiobolin K (8). Ophiobolin K (8) showed cytotoxic activity against various tumor cell lines, including adriamycin-resistant mouse leukemia cells (P388), with IC₅₀ of 0.27-0.65 μM.     

Organic superbase-induced chemiluminescent decomposition of a hydroxyaryl-substituted dioxetane: Unique effect of a bifunctional guanidine base on the chemiluminescence profile of a bicyclic dioxetane bearing a 4-(benzoxazol-2-yl)-3,5-dihydroxyphenyl moiety

Organic superbases represented by TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) effectively induced the decomposition of hydroxyaryl-substituted dioxetanes in acetonitrile to give bright light. The color of the chemiluminescence from a dioxetane bearing a 4-(benzoxazol-2-yl)-3,5-dihydroxyphenyl moiety varied depending on the base used. In addition to this change in the color of emission, TBD increased the chemiluminescence efficiency 2- to 5-fold compared to the results with other base systems and accelerated decomposition of the dioxetane. These unique effects of TBD may be due to its “bifunctional” character, which is different from those of other organic superbases. Chemiluminescent decomposition of the dioxetane was effectively induced by superbases even in apolar p-xylene.     

Color modulation for intramolecular charge-transfer-induced chemiluminescence of bicyclic dioxetanes bearing a 3-hydroxy-5-naphthylphenyl moiety in the coordination sphere

Bicyclic dioxetanes 2a, 2b, and 3, bearing a 3-hydroxy-5-naphthylphenyl moiety underwent charge-transfer-induced decomposition with accompanying emission of light, the color of which changed from red to blue responding to a complex of crown ether with potassium t-butoxide used as a base. Furthermore, they afforded unusual chemiluminescence, the spectra of which displayed two peaks in some cases. It was observed for chemiluminescences in the coordination sphere with crown ether that their spectra did not coincide with the spectra of authentic emitters.     

Automated determination of venlafaxine in human plasma by on‐line SPE‐LC‐MS/MS. Application to a bioequivalence study

A new automated SPE‐LC‐ESI‐MS/MS method was developed and validated to quantify venlafaxine in human plasma using fluoxetine as an internal standard. The analytes were automatically extracted from plasma by C18 SPE cartridges, separated on a C8 RP column and analyzed by MS in the multiple reaction‐monitoring (MRM) mode. The method has a chromatographic run time of 4.0 min and a linear calibration curve over the range of 0.25–200 ng/mL (r >0.997). The between‐run precisions, based on the percent RSD for replicate quality controls (0.75; 80, and 200 ng/mL), were < 8.5% for all concentrations. The between‐run accuracies, based on the percent relative error, were < 4.0%. This method was successfully employed in a bioequivalence study of two venlafaxine capsule formulations (test formulation from Eurofarma (Brazil) and Efexor XR, reference formulation, from Wyeth‐Whitehall, Brazil) in 48 healthy volunteers of both sexes who received a single 150 mg dose of each formulation. More than 3000 samples were analyzed eliminating the analyst's exposure to hazardous organic solvents normally employed in off‐line liquid–liquid extractions. The 90% confidence interval (CI) of the individual ratio geometric mean for Test/Reference was 91.6–103.4% for AUC_{0–48 h} and 102.2–112.6% for C_max. Since both 90% CI for AUC_{0–48 h} and C_max were included in the 80–125% interval proposed by the US Food and Drug Administration (FDA) and the Brazilian National Health Surveillance Agency (ANVISA), the test formulation was considered bioequivalent to Efexor XR according to both the rate and extent of absorption.     

Synthesis and antitumor activity of novel pyrimidinyl pyrazole derivatives. III. Synthesis and antitumor activity of 3-phenylpiperazinyl-1-trans-propenes

A series of novel 3-[4-phenyl-1-piperazinyl]-1-[5-methyl-1-(2-pyrimidinyl)-4-pyrazolyl]-1-trans-propenes and related compounds were synthesized and evaluated by their cytotoxic activity against several tumor cell lines in vitro and in vivo antitumor activity against some tumor models when administered both intraperitoneally and orally. Compounds with the 3-chloropyridin-2-yl group (9g) and the 3-fluoro-5-substituted phenylpiperazinyl group (29b, c, and e) showed significantly potent cytotoxicity by in vitro testing. Among them, the 3-cyano-5-fluorophenyl derivative (29b) exhibited potent antitumor activity against several tumor cells including human carcinoma without causing undesirable effects in mice.     

Synthesis and antitumor activity of novel pyrimidinyl pyrazole derivatives. II. Optimization of the phenylpiperazine moiety of 1-[5-methyl-1-(2-pyrimidinyl)-4-pyrazolyl]-3-phenylpiperazinyl-1-trans-propenes

A series of novel 3-substituted-1-[5-methyl-1-(2-pyrimidinyl)-4-pyrazolyl]-1-trans-propenes in order to improve the in vitro and in vivo activity of our prototype 3-[4-(3-chlorophenyl)-1-piperazinyl]-1-[5-methyl-1-(2-pyrimidinyl)-4-pyrazolyl]-1-trans-propene (2) were synthesized and evaluated by assays of growth inhibition against several tumor cell lines in vitro and antitumor activity against some tumor models when dosed both intraperitoneally and orally in vivo. Compounds 7a and 7e, the 3,5-difluorophenyl and 3,5-dichlorophenyl analogues of 2, respectively, showed significantly more potent cytotoxicity than 2 in vitro and potent antitumor activities without causing decrease of body temperature related to side effects.     

On mechanistic aspects of 5-deazaflavin dependent dehydrogenation of alcohol

The reaction of 5-deazaflavins with alcoholates was investigated and the direct hydride equivalent transfer from C₁ of alcoholates to C₅ of 5-deazaflavins was confirmed by chemical methods. 5-Alkoxy-10-butyl-3-methyl-5-deazaflavins were synthesized by treatment of 10-butyl-5-chloro-3-methyl-5-deazaflavin with the corresponding alcoholates. The 5-alkoxy-5-deazaflavins were reduced by sodium borodeuteride or sodium hydro-sulfite in deuterium oxide or monodeuteriomethanol to give 10-butyl-3-methyl-1,5-dihydro-5-deazaflavin-5,5-D₂ exclusively. 3,10-Dimethyl-5-deazaflavin radical anion was detected by esr technique on treatment of 3,10-dimethyl-5-deazaflavin with potassium in DMF. From the above reactions, a mechanism of 5-deazaflavin dependent dehydrogenation of alcoholate was proposed.     

Marked difference in singlet-chemiexcitation efficiency between syn-anti isomers of spiro[1,2-dioxetane-3,1′-dihydroisobenzofuran] for intramolecular charge-transfer-induced decomposition

Spiro[1,2-dioxetane-3,1′-dihydroisobenzofuran] syn-3 bearing a hydroxy group at the 6-position (as a model syn-rotamer of parent dioxetane 4 bearing a 3-hydroxyphenyl group) and its isomer anti-3 (as a model anti-rotamer of 4) were synthesized. When these spiro-dioxetanes were treated with tetrabutylammonium fluoride (TBAF) in DMSO, anti-3 emitted light with high efficiency (Φ^CL = 0.41), while the respective value for syn-3 was only 1/10 for anti-3. This significant difference in Φ^CL between syn-3 and anti-3 was attributed to the difference in their singlet-chemiexcitation efficiencies.     

Electron-transfer-induced decomposition of 1,2-dioxetanes in negative-mode matrix- assisted laser desorption/ionization time-of-flight mass spectrometry

1,2-Dioxetanes bearing an aromatic electron donor undergo intramolecular charge-transfer-induced chemiluminescence (CTICL). Although there has been some controversy regarding the mechanisms involved, there is little experimental evidence to strongly support any of the proposed mechanisms. In the course of our investigations, to clarify these mechanisms, we tried to effectively ionize dioxetanes bearing a phenolic group and found that poly(3-octylthiophene-2,5-diyl) was a promising matrix for negative-mode matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS). Electron-transfer ionization was found to take place for dioxetanes bearing a hydroxyphenyl moiety that had been further substituted with an aromatic group, which acted as an antenna to catch an electron from the matrix. Furthermore, the characteristic fragmentation of dioxetanes 3c-3d was thought to occur by the elimination of 2-methyl-1-propene (56 u) and pivalaldehyde (86 u) from deprotonated ion [M - H](-) of dioxetanes, based on the results of muliple mass spectrometry measurements of dioxetanes using MALDI quadrupole ion trap ToF-MS. Based on a comparison of fragmentation in dioxetanes and the corresponding keto esters, dioxetanes were presumed to initially generate excited keto esters from which fragmentation took place.     

Crucial dependence of chemiluminescence efficiency on the syn/anti conformation for intramolecular charge-transfer-induced decomposition of bicyclic dioxetanes bearing an oxidoaryl group

Thermally stable rotamers of bicyclic dioxetanes bearing 6-hydroxynaphthalen-1-yl (anti-5a and syn-5a), 3-hydroxynaphthalen-1-yl (anti-5b and syn-5b), and 5-hydroxy-2-methylphenyl groups (anti-5c and syn-5c) were synthesized. These dioxetanes underwent TBAF (tetrabutylammonium fluoride)-induced decomposition accompanied by the emission of light in DMSO and in acetonitrile at 25 °C. For all three pairs of rotamers, the chemiluminescence efficiency Φ(CL) for anti-5 was 8-19 times higher than that for syn-5, and the rate of CTID (charge-transfer-induced decomposition) for anti-5 was faster than that for syn-5. The chemiluminescence spectra of the rotamers for 5a and 5c, respectively, were different. This discrepancy in the chemiluminescence spectra between rotamers can presumably be attributed to the difference in the structures of de novo keto imide anti-14 and syn-14 in an excited state, which inherit the structures of the corresponding intermediary anionic dioxetanes anti-13 and syn-13. The important difference in chemiluminescence efficiency between anti-5 and syn-5 is discussed from the viewpoint of a chemiexcitation mechanism for CTID of oxidophenyl-substituted dioxetane.