A. Durch Kondensation von Na-oxalessigester mit n-Butyraldehyd andÖnanthaldehydund nachfolgende Ketonspaltung wurdenγ-n-Propyl-andγ-n-Hexyl-α-keto-γ-lactonherltellt。
Gas phase synthesis of methylene lactones using catalysts derived from hydrotalcite precursors
申请人:Manzer Ernest Leo
公开号:US20060084818A1
公开(公告)日:2006-04-20
Process for converting certain lactones to their alpha-methylene substituted forms using (i) a catalyst derived from a hydrotalcite or (ii) a composite catalyst comprising the hydrotalcite-derived catalyst into which at least one of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium has been incorporated.
Design of substituted tetrahydrofuran derivatives for HIV-1 protease inhibitors: synthesis, biological evaluation, and X-ray structural studies
作者:Arun K. Ghosh、Daniel Lee、Ashish Sharma、Megan E. Johnson、Ajay K. Ghosh、Yuan-Fang Wang、Johnson Agniswamy、Masayuki Amano、Shin-ichiro Hattori、Irene T. Weber、Hiroaki Mitsuya
DOI:10.1039/d4ob00506f
日期:——
Substituted tetrahydrofuran derivatives were designed and synthesized to serve as the P2 ligand for a series of potent HIV-1 proteaseinhibitors. Both enantiomers of the tetrahydrofuran derivatives were synthesized stereoselectivity in optically active forms using lipase-PS catalyzed enzymatic resolution as the key step. These tetrahydrofuran derivatives are designed to promote hydrogen bonding and van der
Comparison of Two Metal-Dependent Pyruvate Aldolases Related by Convergent Evolution: Substrate Specificity, Kinetic Mechanism, and Substrate Channeling
作者:Weijun Wang、Perrin Baker、Stephen Y. K. Seah
DOI:10.1021/bi100251u
日期:2010.5.4
HpaI and BphI are two pyruvate class II aldolases found in aromatic meta-cleavage degradation pathways that catalyze similar reactions but are not related in sequence. Steady-state kinetic analysis of the aldol addition reactions and product inhibition assays showed that HpaI exhibits a rapid equilibrium random order mechanism while BphI exhibits a compulsory order mechanism, with pyruvate binding first. Both aldolases are able to utilize aldehyde acceptors two to five carbons in length; however, HpaI showed broader specificity and had a preference for aldehydes containing longer linear alkyl chains or C2-OH substitutions. Both enzymes were able to bind 2-keto acids larger than pyruvate, but only HpaI was able to utilize both pyruvate and 2-ketobutanoate as carbonyl donors in the aldol addition reaction. HpaI lacks stereospecific control producing racemic mixtures of 4-hydroxy-2-oxopentanoate (HOPA) from pyruvate and acetaldehyde while BphI synthesizes only (4S)-HOPA. BphI is also able to utilize acetaldehyde produced by the reduction of acetyl-CoA catalyzed by the associated aldehyde dehydrogenase, BphJ. This aldehyde was directly channeled from the dehydrogenase to the aldolase active sites, with an efficiency of 84%. Furthermore, the BphJ reductive deacylation reaction increased 4-fold when BphI was catalyzing the aldol addition reaction. Therefore, the BphI-BphJ enzyme complex exhibits unique bidirectionality in substrate channeling and allosteric activation.
Mechanism of the dehydrogenase reaction of DmpFG and analysis of inter-subunit channeling efficiency and thermodynamic parameters in the overall reaction
作者:Natalie E. Smith、Wan Jun Tie、Gavin R. Flematti、Keith A. Stubbs、Ben Corry、Paul V. Attwood、Alice Vrielink
DOI:10.1016/j.biocel.2013.05.028
日期:2013.8
The bifunctional, microbial enzyme DmpFG is comprised of two subunits: the aldolase, DmpG, and the dehydrogenase, DmpF. DmpFG is of interest due to its ability to channel substrates between the two spatially distinct active sites. While the aldolase is well studied, significantly less is known about the dehydrogenase. Steady-state kinetic measurements of the reverse reaction of DmpF confirmed that the dehydrogenase uses a ping-pong mechanism, with substrate inhibition by acetyl CoA indicating that NAD(+)/NADH and CoA/acetyl CoA bind to the same site in DmpF. The Km of DmpF for exogenous acetaldehyde as a substrate was 23.7 mM, demonstrating the necessity for the channel to deliver acetaldehyde directly from the aldolase to the dehydrogenase active site. A channeling assay on the bifunctional enzyme gave an efficiency of 93% indicating that less than 10% of the toxic acetaldehyde leaks out of the channel into the bulk media, prior to reaching the dehydrogenaSe active site. The thermodynamic activation parameters of the reactions catalyzed by the aldolase, the dehydrogenase and the DmpFG complex were determined. The Gibb's free energy of activation for the dehydrogenase reaction was lower than that obtained for the full DmpFG reaction, in agreement with the high K-cat obtained for the dehydrogenase reaction in isolation. Furthermore, although both the DmpF and DmpG reactions occur with small, favorable entropies of activation, the full DmpFG reaction occurs with a negative entropy of activation. This supports the concept of allosteric structural communication between the two enzymes to coordinate their activities. (C) 2013 Elsevier Ltd. All rights reserved.