5-Aminolaevulinic acid-mediated photodynamic therapy in multidrug resistant leukemia cells

To verify if photodynamic therapy (PDT) could overcome multidrug resistance (MDR) when it it applied to eradicate minimal residual disease in patients with leukemia, we investigated the fluorescence kinetics of 5-aminolaevulinic acid (ALA)-induced protoporphyrin IX (PpIX) and the effect of subsequent photodynamic therapy on MDR leukemia cells, which express P-glycoprotein (P-gp), as well as on their parent cells. Evaluation of PpIX accumulation by flow cytometry showed that PpIX accumulated at higher levels in mdr-1 gene-transduced MDR cells (NB4/MDR) and at lower levels in doxorubicin-induced MDR cells (NOMO-1/ADR) than in their parent cells. A P-gp inhibitor could not increase PpIX accumulation. Measurement of extracellular PpIX concentration by fluorescence spectrometry showed that P-gp did not mediate the fluorescence kinetics of ALA-induced PpIX production. Assessment of ferrochelatase activity using high-performance liquid chromatography indicated that PpIX accumulation in drug-induced MDR cells was probably regulated by this enzyme. Assessment of phototoxicity of PDT using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that PDT was effective in NB4, NB4/MDR, NOMO-1 and NOMO-1/ADR cells, which accumulated high levels of PpIX, but not effective in K562 and K562/ADR cell lines, which accumulated relatively low levels of PpIX. These findings demonstrate that P-gp does not mediate the ALA-fluorescence kinetics, and multidrug resistant leukemia cells do not have cross-resistance to ALA-PDT.     

Total synthesis of (+/-)-stemodinone via an efficient ring-exchange strategy

A total synthesis of (+/-)-stemodinone, a tetracyclic stemodane diterpene, from the known tricyclic methyl olefin 11 is described. The key steps involve an efficient ring-exchange reaction and palladium(0)-catalyzed lactone migration. The ring-exchange strategy for controlling the stereochemistry was based on an initial Diels-Alder reaction to form a new ring followed by cleavage of the original ring. Cleavage of the original ring of the Diels-Alder adduct 9 was achieved by an initial regio- and chemoselective Baeyer-Villiger oxidation followed by the Pd(0)-catalyzed lactone-migration reaction reported by us.     

An efficient synthesis of 5-diethoxymethylimidazole-4-carboxylate,a potential precursor for various imidazole derivatives

Anionic cycloaddition of methyl isocyanoacetate to diethoxyacetonitrile afforded methyl 5-diethoxymethylimidazole-4-carboxylate, a useful imidazole nucleus with two different functional groups.     

A facile synthesis of [3ncyclophanes,in which aromatic rings are connected with -CH2CO-CH2- bridges

The title compounds, I, were synthesized by the dialkylation of TosMIC, II, with appropriate bis (halomethyl) compounds, III, under phase-transfer condition, followed by acid hydrolysis.     

Catalyzed cycloaddition reactions of α-silyloxy-α,β-unsaturated ketone and aldehyde

The reactions of α-silyloxy-ga,β-unsaturated ketone and aldehyde with diene afforded [4+2] and [4+3] cycloadducts respectively in the presence of a catalyst.     

Simple methods for the syntheses of (E)-4- and (E)-5-alkenoic acids by the SN2′ type reactions of γ-vinyl-γ-butyrolactone and δ-vinyl-δ-valerolactone with organocopper reagents

γ-Vinyl-γ-butyrolactone and δ-vinylδ-valerolactone react regio- and stereoselectivity with Grignard reagents in the presence of a copper(I) catalyst or with diorganocuprates to afford (E)-4- and (E)-5-alkenoic acids, respectively, in high yields. Synthetic utility of the former reaction is demonstrated in the simple synthesis of (4E,7Z)-4,7-tridecadienyl acetate.     

NAD(P)+-NAD(P)H model. 38. Reduction of aldehyde by 1,4-dihydroquinolin derivative

Benzaldehyde are reduced to benzyl alcohol by a model compound of NAD(P)H almost quantitatively. Reductions of some other aldehydes are also mentioned.     

A novel synthesis of (E)-3,7-dimethyl-2-octene-1,8-diol secreted by the african monarch using the ring-opening reaction of α-methyl-β-propiolactone

The regioselective ring-opening reaction of α-methyl-β-propiolactone with 3,3-ethylene-dioxybutylmagnesium bromide in the presence of copper(I) catalyst afforded 2-methyl-6-oxoheptanoic acid, which was easily converted into (E)-3,7-dimethyl-2-2-octene-1,8-diol in good yield.     

Topological Structure of the Space of Weighted Composition Operators Between Different Hardy Spaces

We consider properties related to weighted composition operators boundedly acting from the classical Hardy space H ^p to H ^q for \({1 \leq q < p < \infty}\) . Especially, we shall completely determine path connected components in the set of weighted composition operators and explicitly characterize by function-theoretic properties of analytic self-maps.     

Hankel-type operators on the space of bounded harmonic functions

We study Hankel-type operators on the space of bounded harmonic functions on the open unit disk. These operators are related to tight uniform algebras, the Dunford-Pettis property, and Bourgain algebras.