Regiospecific synthesis of mono- and bicyclic 6-alkoxy-2-pyrones and their use in the preparation of substituted aromatics,anthraquinones, and tetracyclic intermediates for 11-deoxyanthracycline synthesis

Several mono- and bicyclic 6-methoxy-2-pyrones having substituents at C4 and C5 can be prepared regiospecifically by either of two routes: (1) regiospecific construction of a glutaconic half-ester followed by dehydrative cyclization, and (2)regiospecific Friedel-Crafts acylation of 6-methoxy-2-pyrones at C5. These pyrones undergo clean and regiospecific Diels-Alder cycloadditions with various unsymmetrical dienophiles, e.g., quinones, unsaturated esters, etc, with subsequent loss of carbon dioxide. In this manner several polycyclic aromatic natural products have been prepared such as chrysophanol, helminthosporin, pachybasin, 2-acetylemodin and the purported structure for orientalone. The utility of this approach for the synthesis of the anthracyclines is demonstrated by its use in the preparation of various tetracyclic intermediates for anthracycline synthesis.     

Isolation of bufotalin 3-suberoyl-histidine and -3-methylhistidine esters from the skin of bufo melanostictus Schneider

Two novel bufotoxins, bufotalin 3-suberoyl-histidine and -3-methyl- histidine esters, were isolated from the skin of the Formosan toad, $\text{Bufo melanostictus}$ Schneider.     

Phase separation of gas–liquid and liquid–liquid microflows in microchips

Phase separation of gas–liquid and liquid–liquid microflows in microchannels were examined and characterized by interfacial pressure balance. We considered the conditions of the phase separation, where the phase separation requires a single phase flow in each output of the microchannel. As the interfacial pressure, we considered the pressure difference between the two phases due to pressure loss in each phase and the Laplace pressure generated by the interfacial tension at the interface between the separated phases. When the pressure difference between the two phases is balanced by the Laplace pressure, the contact line between the two phases is static. Since the contact angle characterizing the Laplace pressure is restricted to values between the advancing and receding contact angles, the Laplace pressure has a limit. When the pressure difference between the two phases exceeds the limiting Laplace pressure, one of the phases leaks into the output channel of the other phase, and the phase separation fails. In order to experimentally verify this physical picture, microchips were used having a width of 215 μm and a depth of 34 μm for the liquid–liquid microflows, a width of 100 μm and a depth of 45 μm for the gas–liquid microflows. The experimental results of the liquid–liquid microflows agreed well with the model whilst that of the gas–liquid microflows did not agree with the model because of the compressive properties of the gas phase and evaporation of the liquid phase. The model is useful for general liquid–liquid microflows in continuous flow chemical processing.     

Rapid Separation of Hydrophobic Compounds by UPLC: in Case of Bisindolylmaleimides, Indolocarbazoles or Fullerene C60 Derivatives

Rapid separation of hydrophobic compounds such as bisindolylmaleimides, indolocarbazoles or fullerene C₆₀ derivatives by ultra performance liquid chromatography was developed. Bisindolylmaleimides and indolocarbazoles were separated within 7 and 5 min, respectively. The linear ranges for the determination of bisindolylmaleimides and indolocarbazoles were 1.25?500 pmol and 0.5?50 pmol per injection (r > 0.99), respectively. Fullerene C₆₀ derivatives were separated within 9 min, and the linear range for the determination of fullerene C₆₀ derivatives was 0.1?10 pmol per injection (r > 0.99).     

Electroorganic synthesis in oil-in-water (O/W) nanoemulsion: TEMPO-mediated electrooxidation of amphiphilic alcohols in water

Oil-in-water nanoemulsion which consisted of TEMPO, amphiphilic alcohols, and water offered unique reaction environments for electrooxidation of the alcohols to give the corresponding carboxylic acids in good to excellent yields.