Reported herein is an inverse-electron-demand
oxa-Diels–Alder reaction that is remotely β,γ-regioselective
with β,γ-unsaturated amides and β,γ-unsaturated-α-ketoesters
using a bifunctional catalyst. It can provide different kinds of dihydropyrans
bearing three subsequent chiral carbon centers in good to high yield
(61–99%) and with complete enantioselectivity (99 to >99%
ee).
Furthermore, a larger-scale experiment confirmed the reliability of
the current reaction, and further effective transformation of the
product has been realized.
An asymmetric cyclization reaction
of azadienes and azlactones
was investigated by employing a Cinchona squaramide
catalyst, which could afford a series of benzofuran-fused six-membered
heterocycles containing a α,α-disubstituted amino acid
unit in a highly diastereoselective (>20:1 dr) and enantioselective
(up to 99% ee) manner with good to excellent yields (up to 92%). A
plausible pathway was proposed to explain the reaction process.
Zanthoxylum nitidum (Roxb.) DC (Rutaceae), called as “liangmianzhen” in China, is well known for its anti-inflammation and analgesic effect. Alkaloids are its main active constituents. However, little has been known about the absorption of main alkaloids in vivo. In this study, an ultra-performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry was employed for identification of absorbed alkaloids in rats after oral administration of Z. nitidum decoction. By analyzing the fragmentation patterns, a total of nineteen alkaloids were exactly or tentatively identified in rat plasma after treatment, of which magnoflorine, α-allocryptopine, and skimmianine are dominant. Moreover, a high performance liquid chromatography coupled mass spectrometry method was developed for simultaneous quantification of magnoflorine, α-allocryptopine, and skimmianine, and successfully applied to pharmacokinetic study in rats after oral administration of Z. nitidum decoction. The research would contribute to comprehensive understanding of the material basis and function mechanism of Z. nitidum decoction.
Identification of α-Amyrin 28-Carboxylase and Glycosyltransferase From Ilex asprella and Production of Ursolic Acid 28-O-β-D-Glucopyranoside in Engineered Yeast.
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