Salicylaldehyde as an SET-HAT Bifunctional Photocatalyst for the Intermolecular Transalkylation of Phthalimide.

Salicylaldehyde works as an efficient photocatalyst for the intermolecular transalkylation of phthalimide. The well-designed dimethyl N-hydroxyphthalimide ester proves to be a good alkylation reagent. It inhibits the competing intramolecular alkylation of alkylating reagent, enabling the site-specific synthesis of N-substituted phthalimide.

Iron-Catalyzed Aerobic α,ß-Dehydrogenation.

An iron-catalyzed direct aerobic α,ß-dehydrogenation of carbonyls has been reported. The combination of tert-butyl nitrite and N-hydroxyphthalimide worked as the organo cocatalyst system; thus, no extra transition metal reagents are required. A large variety of lactams and flavanones as well as lactone and thiochromen-4-one could be produced via this method in high yields.

Endo/Exo-Controllable Photocyclization by EnT-SET-Switch.

CBZ6, a redox-neutral non-donor-acceptor-type organo-photocatalyst, presents a strong reductive potential with an oxidative potential of -2.16 V (vs SCE). It can work as a photosensitizer for both single-electron transfer and triplet energy transfer processes. This feature enables site-selective control in the intramolecular hydroarylation of acrylamides. Both 5-exo-trig and 6-endo-trig cyclization products could be prepared regiospecfically under mild conditions. No transition metal, halogen-containing reagents, or additional reductant or oxidant is involved. This process provides a concise and environmentally sustainable access to a series of oxindoles and dihydroquinolinones.

Direct Synthesis of ß-Amino Aldehydes from Linear Allylic Esters Using O2 as the Sole Oxidant.

A tandem isomerization-anti-Markovnikov oxidation of linear allylic imidic esters is developed using bis(benzonitrile)palladium chloride as the catalyst and O2 as the sole oxidant, regiospecifically giving ß-amino aldehydes as the product. tert-Butyl nitrite works as a simple, and the only, redox cocatalyst. tBuOH proves to be a crucial solvent for achieving excellent yield and specificity toward anti-Markovnikov aldehyde products.

[Quantitation & optimization of guanosine fermentation process: prevention of NH4+ accumulation increases guanosine production by 70%].

Metabolic engineering has become a powerful tool for optimization of industrial fermentation processes. Metabolic engineering usually undergoes three steps: construction of a recombinant strain with improved properties, genetic and biochemical analysis of the strain, and identification of target for further improvement. Metabolic fluxes analysis is an important part of the biochemical analysis. Based on the law of mass conservation and assuming pseudo-steady-state for the intermediates in the metabolic pathways, we have quantitatively analyzed the time course of the flux distribution in Bacillus subtilis and used the data to reveal the nature of the so-called "40 hour" phenomenon in fermentation of guanosine, a key raw material for the synthesis of additives for human consumption and animal feeds. The phenomenon refers to the observation that guanosine production, which proceeds at high rate from 12 hour on, declines around 40 hour while consumption of glucose keeps increasing, leading to the lower yield of the nucleoside. Equations based upon the metabolic network of Bacillus subtilis consisted of EMP pathway, HMP pathway, TCA cycle, oxidative phosphorylation pathway and others reactions of the intermediates, was constructed. The equations were solved by using the quantitative data obtained in this study. The air flow and volume, concentration of oxygen and carbon dioxide in the exit-gas were monitored online; the concentration of biomass, glucose and guanosine was analyzed manually; and the concentration of acetate, citric acid, pyruvate, and 17 amino acids were HPLC quantified. The solutions of the equation were proved to be valid, as the experimental data on oxygen consumption agrees with that of predicted form the equation. The results indicated that at 40h of the fermentation process the flux of HMP pathway, which provides the precursor of the nucleoside, decreased while that of EMP pathway and the pathways that generate amino acids and organic acids increased. The shift correlated with the accumulation of NH4+ in the broth. The assimilation of NH4+ is an energy consuming process and could shift the metabolism to the energy generating EMP pathway. Accordingly, measures were taken to prevent the accumulation of NH4+. The interference indeed stopped the metabolism shift and boosted the guanosine production at 30 g/L, 70% higher than the level reported in literature.

[Analysis on metabolic flux shift during guanosine fermentation].

Taking the typical metabolic control product-guanosine as an example, the method of metabolic flux shift investigation based on process multi-levels parameter correlation analysis was established. The metabolic pathway, multi-parameter correlation, accumulation of amino acid and organic acid during guanosine fermentation process were integratively analyzed. The metabolic flux shift from HMP to EMP was ascertained, which was assumed to be caused by the accumulation of ammonium ion. The subsequent optimization based on controlling flux distribution between EMP and HMP did improve the yield by 35% when the metabolic flux shift was prevented.