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On Biocatalysis as Resourceful Methodology for Complex Syntheses: Selective Catalysis, Cascades and Biosynthesis
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Andreas Sebastian Klein, Thomas Classen, Jörg Pietruszka
Statins decrease the cholesterol level and were blockbuster par excellence in affluent societies. Especially the chiral side-chain of atorvastatin (11) has been synthesized by many groups using biocatalysis with great success (Patel, 2009; Müller, 2004). The chemical company DSM was able to implement a multi-ton scale production based on the 2-deoxy-ribose-5-phosphate aldolase (DERA), which naturally cleaves the name giving substrate into acetaldehyde and glyceraldehyde-3-phosphate (Haridas et al., 2018). Since enzymes accelerate a given reaction but do not influence the thermodynamic equilibrium, the DERA can also be used in the aldol rather than the retro-aldol reaction (see Fig. 21.3). The precursor of the side-chain 9 can be produced in one reaction sequence, where DERA performs two consecutive aldol reactions: the first between acetaldehyde (7) and chloroacetaldehyde (8), and the second between previously formed aldol (8) and second molecule of acetaldehyde (7). The formed lactol 10 can be transformed into the respective pharmacophore of atorvastatin (11). This process takes advantage of DERA’s chemo- and stereoselectivity.
Hazard Assessment
Published in Leon Golberg, Hazard Assessment of Ethylene Oxide, 2017
Hathway232 attributes the mechanism of carcinogenesis and mutagenesis of vinyl chloride to imidazo-cyclization of deoxyadenosine (dA) and deoxycytidine (dC) in rat liver DNA, forming the relatively persistent product etheno-dC and the less persistent etheno-dA. These adducts induce transversions which are consistent with base-pair-substitution (BPS) mutations induced by metabolically activated vinyl chloride, chloroethylene oxide and chloroacetaldehyde. As noted in , EO induces BPS mutations without activation, especially in Salmonella typhimurium strain TA 1535.
Physical Properties of Individual Groundwater Chemicals
Published in John H. Montgomery, Thomas Roy Crompton, Environmental Chemicals Desk Reference, 2017
John H. Montgomery, Thomas Roy Crompton
Chemical/Physical. In a laboratory experiment, it was observed that the leaching of a vinyl chloride monomer from a polyvinyl chloride pipe into water reacted with chlorine to form chloroacetaldehyde, chloroacetic acid, and other unidentified compounds (Ando and Sayato, 1984).
Overview of biological mechanisms of human carcinogens
Published in Journal of Toxicology and Environmental Health, Part B, 2019
Nicholas Birkett, Mustafa Al-Zoughool, Michael Bird, Robert A. Baan, Jan Zielinski, Daniel Krewski
Vinyl chloride is readily absorbed upon inhalation and rapidly metabolized in the liver. The primary metabolites are highly reactive chloroethylene oxide, and its rearrangement product chloroacetaldehyde. Both bind to proteins, DNA and RNA and form ethenoadducts. Chloroethylene oxide is the most reactive with nucleotides. Vinyl chloride is mutagenic, usually in the presence of metabolic activation, in various assays with bacteria, yeast or mammalian cells. This compound is also clastogenic in vivo and in vitro. Vinyl chloride induces unscheduled DNA synthesis, increases the frequency of sister chromatid exchange in rat and human cells, and elevates the frequency of chromosomal aberrations, DNA strand breaks and micronucleus formation in mice, rats, and hamsters in vivo. Polymorphic variations in metabolic genes (e.g. those of the CYP450 family) or DNA repair genes may alter carcinogenicity but do not affect the underlying mechanisms.
Quantum chemical study on ·Cl-initiated degradation of ethyl vinyl ether in atmosphere
Published in Molecular Physics, 2020
Dandan Han, Haijie Cao, Fengrong Zhang, Maoxia He
Schematic potential energy surfaces for the subsequent reactions of IM13 are depicted in Figure 5. H atom could be abstracted from C3 directly or with the help of O2 molecular. Both pathways, forming ethyl chloroacetate (P1), are prone to occur because of the lower energy barriers (10.39 and 15.85 kcal mol−1). The third pathway is the cleavage of C1–C2 single bond and synchronous formation of C2 = O2 double bond. Ethyl formate (P2) and ClCH2 radical (IM14) are formed with the energy barrier of 4.23 kcal mol−1 and the reaction heat of −9.94 kcal mol−1. The fourth dissociation reaction of IM13 is the bond breaking of C2-O1 and the formation of C2 = O2, leading to the generation of 2-chloroacetaldehyde (P5) and OC2H5 radical. The energy barrier and reaction heat of this route are 21.46 and 11.72 kcal mol−1, respectively. The last process is the formation of alcohol (P7) and IM19 via the rupture of C2-O1 and the H-shift from C2 to O1 atom, with the energy barrier of 13.66 kcal mol−1 and the exothermic heat of 0.80 kcal mol−1. The subsequent pathways of IM14, IM18 and IM19 could form formyl chloride (P3), formaldehyde (P4) and acetaldehyde (P6), which have been discussed in our previous work [58,59]. Comparing the energy barriers and the reaction heats of the further reactions of IM13, we can draw a conclusion that ethyl chloroacetate (P1), ethyl formate (P2), formyl chloride (P3) and formaldehyde (P4) are the most favourable products, while 2-chloroacetaldehyde (P5), acetaldehyde (P6) and alcohol (P7) are secondary products.