Panax notoginseng is one of the
most famous valuable medical plants in China, and its broad application
in clinical treatment has an inseparable relationship with the active
molecules, ginsenosides. Ginsenosides are glycoside compounds that
have varied structures for the diverse sugar chain. Although extensive
work has been done, there are still unknown steps in the biosynthetic
pathway of ginsenosides. Here, we screened candidate glycosyltransferase
genes based on the previous genome and transcriptome data of P. notoginseng and cloned the full length of 27 UGT
genes successfully. Among them, we found that PnUGT33
could catalyze different ginsenoside substrates to produce higher
polarity rare ginsenosides by extending the sugar chain. We further
analyzed the enzymatic kinetics and predicted the catalytic mechanism
of PnUGT33 by simulating molecular docking. After
that, we reconstructed the biosynthetic pathway of rare ginsenoside
Rg3 and gypenoside LXXV in yeast. By combining the Golden
Gate method and overexpressing the UDPG biosynthetic genes, we further
improved the yield of engineering yeast strain. Finally, the shake-flask
culture yield of Rg3 reached 51 mg/L and the fed-batch
fermentation yield of gypenoside LXXV reached 94.5 mg/L, which was
the first and highest record.
Chiral magnesium catalyzed intramolecular vinylogous Michael reaction of novel cyclohexadienones via a desymmetrization process is reported. (R)-BINOL derived ligand and an achiral amide were employed in the current in situ generated magnesium catalyst, giving the corresponding hydrogenated benzofuranone skeletons in good to excellent enantioselectivities with high yields. This simple and efficient strategy could be utilized for the synthesis of aromatized α,β-unsaturated ester and Br-substituted hydrogenated benzofuranone in good yields under mild conditions. Letter pubs.acs.org/OrgLett
Efficient
regioselective synthesis of novel fully substituted pyrazoles
has been achieved through Huisgen cycloaddition reaction of δ-acetoxy
allenoates with hydrazonoyl chlorides by the addition of Ag2O. The present approach offers the advantages of simpleness, high
efficiency, mild conditions, wide substrate scope, and good-to-excellent
regioselectivities. The strategy could be performed on a large-scale
pattern to allow access to structurally versatile pyrazoles, of which
a key intermediate of lonazolac (303), a nonsteroidal anti-inflammatory
drug, could be synthesized efficiently. Moreover, several pyrazoles
show obvious growth-inhibitory activity of Huh-7 cells, expected as
potential anticancer agents.
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