A p68 reductase participating in the asymmetric reduction of the C–C double bond of 2-substituted 2-butenolides was isolated from Marchantia polymorpha. The enzyme reduced 2-substituted 2-butenolides to give (R)-butanolides, and the reduction of citraconic anhydride afforded (R)-methylsuccinic anhydride. 相似文献
Cycloalkanone (C5–C8, C12, and C15) or cycloalkane (C5 and C6) ring-containing monomeric diesters and the polyesters derived from them were prepared, and their configurations were studied by 13C-NMR spectroscopy. Absolute configurations were determined for ring sizes 5, 6, and 7. Configurational change during reduction of a ketonic group of monomeric diesters with ring sizes 5 and 6 was discussed in terms of the steric effect of ring substituents on the ketonic group. In the polycondensation reaction epimerization of the ring units was observed in 5-, 6-, and 7-membered cycloalkanones and not in others, which is explained by steric hindrance by the ring substituents against attack of tetrabutyl titanate catalyst on the ketonic group. 相似文献
A series of 9,10-dihydro-9,10-(1,2-tropylio)anthracene tetrafluoroborates has been prepared. The intramolecular charge-transfer interactions in were confirmed by their UV spectra and pKR+ values. As a model compound 1,2,3,4-tetrahydro-1,4-(1,2-tropylio)naphthalene tetrafluoroborate ()_was also examined. 相似文献
Cultured plant cells of Marchantia polymorpha, Nicotiana tabacum, Phytolacca americana, Catharanthus roseus, and Gossypium hirsutum were examined for their ability to reduce curcumin. Only M. polymorpha cells converted curcumin into tetrahydrocurcumin in 90% yield in one day. Time-course experiment revealed a two-step formation of tetrahydrocurcumin via dihydrocurcumin. 相似文献
Molecular relaxations of polyesters containing C5–C15 rings in the main chain have been studied by DSC, dielectric dispersion, and NMR. Results are discussed in relation to the size and mobility of the rings. The Tg or α-relaxation peak moves to higher temperature with an increase in the ring size from C5 to C12, but the effect is accompanied by an even–odd alternation with ring size. The β relaxations in dielectric dispersion reflect local-mode motion of ester groups and are affected by steric interactions with the rings. Motions of the ring methylenes of C12 and C15 ring units are detected below Tg by broad-line NMR. 相似文献
Three new docetaxel prodrugs, i.e., 7-propionyldocetaxel 3'-O-β-D-glycopyranosides, which contain ester-linked monosaccharides, were synthesized by a chemo-enzymatic procedure involving enzymatic transglycosylations with lactase, β-galactosidase, or β-xylosidase. The water-solubility of 7-propionyldocetaxel 3'-O-β-D-glucopyranoside was 52-fold higher than that of docetaxel. 7-Propionyldocetaxel 3'-O-β-D-glucopyranoside and 7-propionyldocetaxel 3'-O-β-D-xylopyranoside were effectively hydrolyzed by the relevant enzyme(s) of human cancer cells to release docetaxel, whereas 7-propionyldocetaxel 3'-O-β-D-galactopyranoside was relatively resistant under similar conditions. 7-Propionyldocetaxel 3'-O-β-D-glucopyranoside and 7-propionyldocetaxel 3'-O-β-D-xylopyranoside showed in vitro cytotoxic activity against human cancer cells, whereas 7-propionyldocetaxel 3'-O-β-D-galactopyranoside exerted low cytotoxicity. 相似文献
Glycosylation of vanilloids such as vanillin and 8-nordihydrocapsaicin by cultured plant cells of Eucalyptus perriniana was studied. Vanillin was converted into vanillin 4-O-β-D-glucopyranoside, vanillyl alcohol, and 4-O-β-D-glucopyranosylvanillyl alcohol by E. perriniana cells. Incubation of cultured E. perriniana cells with 8-nordihydrocapsaicin gave 8-nordihydrocapsaicin 4-O-β-D-glucopyranoside and 8-nordihydrocapsaicin 4-O-β-D-gentiobioside. 相似文献
An electric double-layer capacitor (EDLC) was assembled with the polymer hydrogel electrolyte prepared from cross-linked potassium
poly(acrylate) (PAAK) and KOH aqueous solution, and the self-discharge characteristics were investigated. The EDLC cell with
the polymer hydrogel electrolyte showed lower voltage decay on open circuit than that with a KOH aqueous solution. Moreover,
it was found that the leakage current of the EDLC cell was markedly suppressed by using the polymer hydrogel electrolyte.
The suppression was enhanced with increasing PAAK content in the electrolyte. These results strongly suggest that the PAAK
plays an important role in the suppression of self-discharge. 相似文献