Enantioselective Synthesis of Biarylphenylglycines and Their Use as Chiral Ligands in the Lewis Acid Catalyzed Diels-Alder Reaction

The enantioselective syntheses of naphthyl-substituted-N-tosylphenylglycines are described. These unnatural amino acids were tested as ligands for the chiral oxazaborolidine catalyzed Diels-Alder reaction between cyclopentadiene and 2-bromoacrolein.     

Effects of a heavy metal (zinc) on organic adsorption capacity and organic removal in activated sludge

Applied Biochemistry and Biotechnology - Effects of a common heavy metal (zinc) on activated sludge were studied with a sequencing batch reactor (SBR). Organic removal in activated sludge was...     

Accumulation of biodegradable copolyesters of 3-hydroxy-butyrate and 3-hydroxyvalerate inAlcaligenes eutrophus

Applied Biochemistry and Biotechnology - Biodegradable copolyesters of 3-hydroxybutyrate-co-3-hydroxyvalerate (3HB-3HV) were produced byAlcaligenes eutrophus in a two-staged process, namely growth...     

Interaction of lithium hydride and ammonia borane in THF

The two-step reaction between LiH and NH(3)BH(3) in THF leads to the production of more than 14 wt% of hydrogen at 40 degrees C.     

A highly stereoselective organocatalytic tandem aminoxylation/aza-Michael reaction for the synthesis of tetrahydro-1,2-oxazines

A facile stereoselective synthesis of multifunctionalized tetrahydro-1,2-oxazines (THOs) has been achieved by the organocatalyzed asymmetric tandem alpha-aminoxylation/aza-Michael reaction for the C-O/C-N bond formations in moderate to good yields with excellent diastereo- (>99:1 dr) and enantioselectivities (92% to >99% ee).     

Control of four stereocenters in an organocatalytic domino double Michael reaction: efficient synthesis of multisubstituted cyclopentanes

A highly enantioselective and diastereoselective domino organocatalytic double Michael reaction which provides expedited access to multifunctionalized five-membered rings catalyzed by 9-amino-9-deoxyepiquinine (V) has been developed. Simple operational procedures, high yields (81-92%), excellent enantioselectivity (90-97% ee), diastereoselectivities (95:5->99:1 dr), and immense potential of synthetic versatility of the products render this new methodology highly appealing for asymmetric synthesis.     

Effects of trace levels of copper,chromium, and zinc ions on the performance of activated sludge

The effects of copper, chromium, and zinc ions, at trace levels, on the performance of a simulated activated sludge process were investigated. The results of batch adsorption experiments showed that the adsorption of copper, chromium, and zinc ions followed both the Langmuir and Freundlich isotherms. The presence of trace levels of these three metals not only reduced the adsorption rate of organic matters but also the chemical oxygen demand adsorption capacity (CAC) of the activated sludge. Metal ions competed with the organic substrate for adsorption binding sites on the surfaces of activated sludge bioflocs and reduced the CAC. Studies performed in a sequential batch reactor (SBR) showed that the presence of trace levels of heavy metal ions in wastewater affected the SBR performance to different extents depending on the hydraulic retention time (HRT). When the reactors were operated at short HRTs of 2.5 d or less, the presence of trace levels of heavy metal ions reduced substantially the CAC of activated sludge, which, in turn, affected significantly the performance of the SBR. However, under longer HRTs (e.g., 5d), the heavy metal ions in the wastewater reduced the CAC but had not significant effect on the chemical oxygen demand removal efficiency.     

Optimal production of polyhydroxyalkanoates in activated sludge biomass

Polyhydroxyalkanoates (PHAs) have been recognized as good candidates for biodegradable plastics, but their high price compared with conventional plastics has limited their use. In this study, actiated sludge microorgan isms from a conventional wastewater treatment process were induced, bycontrol-lingthe carbon: nitrogen (C:N) ratioin the reacorliquor, toaccumulate PHAs. In addition, an intermittent nitrogen feeding program was established to optimize the volumetric PHA productivity in a wastewater treatment process. The optimal overall polymer production yield of 0.111 g of polymer/g of carbonaceous substrate consumed was achieved under a C:N ratio of 96:1 by feeding nitrogen in the reactor liquor onceevery four cycles. At the same time, the amount of excess sludge generated from the wastewater treatment process was reduced by22.9%.