Viridaphin A1 glucoside, a green pigment possessing cytotoxic and antibacterial activity from the aphid Megoura crassicauda.

A green pigment, viridaphin A1 glucoside (1), was isolated from the green aphid Megoura crassicauda. One- and two-dimensional NMR spectrometric analyses of 1 and its aglycone established the structure as an octacyclic compound. Viridaphin A1 glucoside exhibited cytotoxicity against HL-60 human tumor cells with an IC50 of 23 µM and antibacterial activity against Bacillus subtilis NBRC 3134 with a minimum inhibitory concentration of 10.0 µg/mL. These results suggested that aphid pigments may protect aphids from invasive species, including viruses and bacteria.

A practical total synthesis of (+)-antimycin A9.

(+)-Antimycin A9 (AA9) isolated from a cultured broth of Streptomyces sp. K01-0031 was synthesized via an asymmetric aldol reaction using Oppolzer's sultam as a chiral auxiliary.

Evidence of ROS generation by mitochondria in cells with impaired electron transport chain and mitochondrial DNA damage.

Mitochondrial damage is a well known cause of mitochondria-related diseases. A major mechanism underlying the development of mitochondria-related diseases is thought to be an increase in intracellular oxidative stress produced by impairment of the mitochondrial electron transport chain (ETC). However, clear evidence of intracellular free radical generation has not been clearly provided for mitochondrial DNA (mtDNA)-damaged cells. In this study, using the novel fluorescence dye, 2-[6-(4'-hydroxy)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (HPF), which was designed to detect hydroxyl radicals (*OH), intracellular free radical formation was examined in 143B cells (parental cells), 143B-rho(0) cells (mtDNA-lacking cells), 87 wt (cybrid), and cybrids of 4977-bp mtDNA deletion (common deletion) cells containing the deletion with 0%, 5%, 50% and >99% frequency (HeLacot, BH5, BH50 and BH3.12, respectively), using a laser confocal microscope detection method. ETC inhibitors (rotenone, 3-nitropropionic acid, thenoyltrifluoroacetone, antimycin A and sodium cyanide) were also tested to determine whether inhibitor treatment increased intracellular reactive oxygen species (ROS) generation. A significant increase in ROS for 143B-rho(0) cells was observed compared with 143B cells. However, for the 87 wt cybrid, no increase was observed. An increase was also observed in the mtDNA-deleted cells BH50 and BH3.12. The ETC inhibitors increased intracellular ROS in both 143B and 143B-rho(0) cells. Furthermore, in every fluorescence image, the fluorescence dye appeared localized around the nuclei. To clarify the localization, we double-stained cells with the dye and MitoTracker Red. The resulting fluorescence was consistently located in mitochondria. Furthermore, manganese superoxide dismutase (MnSOD) cDNA-transfected cells had decreased ROS. These results suggest that more ROS are generated from mitochondria in ETC-inhibited and mtDNA-damaged cells, which have impaired ETC.

Preparation of (Cyanomethylene)tributylphosphorane: a new mitsunobu-type reagent.

(Cyanomethylene)tributylphosphorane (CMBP), which promoted the alkylation of various nucleophiles (HA) with alcohols (ROH) to give RA (Mitsunobu-type reaction), was prepared in two steps starting from chloroacetonitrile.

Heteroatom-guided torquoselective olefination of alpha-oxy and alpha-amino ketones via ynolates.

Ynolates were found to react with alpha-alkoxy-, alpha-siloxy-, and alpha-aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the beta-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z selectivity is induced by orbital and steric interactions rather than by chelation. In a similar manner, alpha-dialkylamino ketones provided olefins with excellent Z selectivity. These products can be easily converted into multisubstituted butenolides and gamma-butyrolactams in good yield.