Pd/NHC sequentially catalyzed atroposelective synthesis of planar-chiral macrocycles.

Planar-chiral macrocycles play a pivotal role in host-guest chemistry and drug discovery. However, compared with the synthesis of other types of chiral compounds, the asymmetric construction of planar-chiral macrocycles still remains a forbidding challenge. Herein, we report a sequential palladium and N-heterocyclic carbene catalysis to build planar-chiral macrocycles.

Extracellular Expression of Feruloyl Esterase and Xylanase in for Ferulic Acid Production from Agricultural Residues.

There is still a large amount of ferulic acid (FA), an outstanding antioxidant, present in agricultural residues. Enzymatic hydrolysis has been regarded as the most effective way to release FA. This present study therefore selected feruloyl esterase (FAE) and xylanase (XYN) from the metagenomes of a cow rumen and a camel rumen, respectively, for their recombinant expression in BL21 and further application in releasing FA.

Synthesis and in vitro antitumour activity of 4(R)-methyl-3-O-phosphonomethyl-α-l-threose nucleosides.

A series of novel α-l-threose nucleoside phosphonate analogs, 4(R)-methyl-3-O-phosphonomethyl-α-l-threose nucleosides, were synthesized in multistep sequences starting from d-xylose. The synthetic sequence consisted of the following key stages: (i) the multistep synthesis of 1,2-O-isopropylidenyl-4(R)-methyl-3-O-phosphonomethyl-l-threose, (ii) the transformation of 1,2-O-isopropylidenyl sugar into suitable 1,2-di-O-acyl l-threose precursor, and (iii) the construction of target α-l-threose nucleoside phosphonate analogs by Vorbrüggen glycosidation reaction, deprotection of acyl group, and hydrolysis of diethyl group on phosphonate. The target nucleoside phosphonates were evaluated for their antitumour activities in cell culture-based assays.