Enhanced production of shikimic acid using a multi-gene co-expression system in Escherichia coli.

Shikimic acid (SA) is the key synthetic material for the chemical synthesis of Oseltamivir, which is prescribed as the front-line treatment for serious cases of influenza. Multi-gene expression vector can be used for expressing the plurality of the genes in one plasmid, so it is widely applied to increase the yield of metabolites. In the present study, on the basis of a shikimate kinase genetic defect strain Escherichia coli BL21 (ΔaroL/aroK, DE3), the key enzyme genes aroG, aroB, tktA and aroE of SA pathway were co-expressed and compared systematically by constructing a series of multi-gene expression vectors. The results showed that different gene co-expression combinations (two, three or four genes) or gene orders had different effects on the production of SA. SA production of the recombinant BL21-GBAE reached to 886.38 mg·L(-1), which was 17-fold (P < 0.05) of the parent strain BL21 (ΔaroL/aroK, DE3).

Palladium/copper-catalyzed oxidative arylation of terminal alkenes with aroyl hydrazides.

An unprecedented oxidative arylation reaction of terminal alkenes with simple aroyl hydrazides has been developed under aerobic conditions for the stereoselective synthesis of 1,2-disubstituted alkenes. A range of aroyl hydrazides underwent palladium/copper-catalyzed oxidative Mizoroki-Heck reaction with terminal alkenes open to air in a 1:1 mixture of dimethyl sulfoxide and acetonitrile to give structurally diverse 1,2-disubstituted alkenes in moderate to excellent yields with excellent regio- and E-selectivity. The reaction tolerated a wide variety of functional groups, such as alkoxy, hydroxy, amino, fluoro, chloro, bromo, cyano, nitro, ester, amide, imide, phosphine oxide, and sulfone groups, and, moreover, molecular oxygen and dimethyl sulfoxide were demonstrated to serve as terminal oxidants. This study provides a useful method for the stereoselective synthesis of 1,2-disubstituted alkenes through direct transformation of the vinylic CH bonds in terminal alkenes.