36960-22-2Relevant academic research and scientific papers
Enantioselective Cascade Biocatalysis for Deracemization of Racemic β-Amino Alcohols to Enantiopure (S)-β-Amino Alcohols by Employing Cyclohexylamine Oxidase and ω-Transaminase
Zhang, Jian-Dong,Chang, Ya-Wen,Dong, Rui,Yang, Xiao-Xiao,Gao, Li-Li,Li, Jing,Huang, Shuang-Ping,Guo, Xing-Mei,Zhang, Chao-Feng,Chang, Hong-Hong
, p. 124 - 128 (2020/09/21)
Optically active β-amino alcohols are very useful chiral intermediates frequently used in the preparation of pharmaceutically active substances. Here, a novel cyclohexylamine oxidase (ArCHAO) was identified from the genome sequence of Arthrobacter sp. TYUT010-15 with the R-stereoselective deamination activity of β-amino alcohol. ArCHAO was cloned and successfully expressed in E. coli BL21, purified and characterized. Substrate-specific analysis revealed that ArCHAO has high activity (4.15 to 6.34 U mg?1 protein) and excellent enantioselectivity toward the tested β-amino alcohols. By using purified ArCHAO, a wide range of racemic β-amino alcohols were resolved, (S)-β-amino alcohols were obtained in >99 % ee. Deracemization of racemic β-amino alcohols was conducted by ArCHAO-catalyzed enantioselective deamination and transaminase-catalyzed enantioselective amination to afford (S)-β-amino alcohols in excellent conversion (78–94 %) and enantiomeric excess (>99 %). Preparative-scale deracemization was carried out with 50 mM (6.859 g L?1) racemic 2-amino-2-phenylethanol, (S)-2-amino-2-phenylethanol was obtained in 75 % isolated yield and >99 % ee.
Bacterial biotransformation of isoprene and related dienes
Boyd, Derek R.,Clarke, David,Cleij, Marcel C.,Hamilton, John T.G.,Sheldrake, Gary N.
, p. 673 - 685 (2007/10/03)
The bacterium Pseudomonas putida ML 2 was used in the oxidative biodegradation of the acyclic dienes isoprene, trans-piperylene, cis-piperylene, and 1,3-butadiene. Regioselective dioxygenase-catalyzed dihydroxylation of alkenes yielded vicinal diols in the preferred sequence monosubstituted 〉 cis-disubstituted 〉 gem-disubstituted 〉 trans-disubstituted. The isolated diol metabolites had an excess of the R configuration (9-97% ee), and further diol oxidation was controlled by addition of propylene glycol as an inhibitor. Stereoselectivity using the ML2 strain resulted from both enzymatic asymmetric alkene dihydroxylation and kinetic resolution of diols. Enantioselective oxidation of the allylic secondary alcohol group of R configuration yielded the corresponding unsaturated ketoalcohol; the residual diol was recovered with a large excess (≥ 93% ee) of the S configuration. In addition to the enzymatic diene oxidation steps yielding unsaturated diols and ketoalcohols, evidence was also found of enzymatic alkene hydrogenation to yield saturated ketoalcohols and diols.
Product distributions from the OH radical-induced oxidation of but-1-ene, methyl-substituted but-1-enes and isoprene in NO(x)-free air
Benkelberg,Boge,Seuwen,Warneck
, p. 4029 - 4039 (2007/10/03)
Product distributions resulting from the OH-induced oxidation of but-1-ene, 2-methylbut-1-ene, 3-methylbut-1-ene and isoprene in air were measured in the absence of nitrogen oxides and compared with predictions based on currently accepted oxidation mechanisms. In the case of butenes, the observed distributions of carbonyl compounds, hydroxyketones, hydroxyalkanals and diols were evaluated to obtain probabilities for the initial attack of OH radical on the outer position of the double bond (y = 0.90 ± 0.03 for 2-Me-but-1-ene and y = 0.76 ± 0.05 for both but-1-ene and 3-Me-but-1-ene), for the probability of formation of stable products in the self-reaction of secondary β-hydroxyperoxyl radicals (k(ssb)/k(ss) = 0.29 ± 0.07 for but-1-ene and k(ssb)/k(ss) = 0.19 ± 0.06 for 3-Me-but-1-ene), and for the ratio of the reaction with oxygen vs. decomposition of β-hydroxyalkoxyl radicals, k3[O2]/(k4 + k3[O2]) = 0.25 ± 0.04 for but-1-ene and = 0.38 ± 0.04 for 3-Me-but-1-ene. The last two values disagree with other published data, which suggest a smaller effect of oxygen. The oxidation of isoprene produced methacrolein and methyl vinyl ketone with a ratio 0.93 ± 0.10, the ratio of methyl vinyl ketone and 3-methylfuran was 7.3 ± 1.0. Other products were 1-hydroxy-3-methylbut-3-en-2-one (identified by mass spectrometry) and 3-methyl-3-oxo-butane (tentatively identified). The overall product distribution was complex and could not be fully elucidated. Computer simulations based on several mechanisms applied the relative probabilities for OH addition found for the but-1-enes. Comparison with the experimental data suggests probabilities for OH addition to the methylated double bond of 0.504 ± 0.027 (outer position) and 0.056 ± 0.003 (inner position), and to the non-methylated double bond of 0.335 ± 0.023 (outer position) and 0.105 ± 0.008 (inner position).
Reactivity of α,α′-dichloroketones towards anions electrogenerated at carbonium and oxygen atoms. Electrochemically-induced Favorskii rearrangement. Part 2
Chiarotto, Isabella,Feroci, Marta,Giomini, Claudio,Inesi, Achille
, p. 167 - 175 (2007/10/03)
Electrolyses of solutions containing α,α′-dichloroketones 1a or 2a were carried out, on a mercury pool or glassy carbon cathode, at a potential sufficiently negative to allow two-electron cleavage of the C-Cl bond. The effects of the presence of carboxylic acids 3a,b, phenols 4a-f, or carbon acid 5 in the solutions were evaluated. Depending on the type of acidic substrate, it was possible to isolate from the cathodic solutions the Favorskii-rearrangement products 9m, 10m, 11 and 12, as well as dechlorinated ketones 1b and 2b and the addition products 7m and 8m. The conditions under which it was possible, by electrochemical means, to induce the Favorskii rearrangement between dichloroketones 1a and 2a and the acidic substrates are discussed. Evidence was gained by voltammetric analysis that the rates of formation of the Favorskii adducts 9a-f depend on the structures of the corresponding phenols 4a-f. By employing electrogenerated bases, it was possible to obtain α,β-unsaturated ketones at potentials less negative than required for the direct reduction of 1a and 2a. Elsevier.
Selectivity in the Oxidation of Aliphatic Ketones by Thallic Sulphate in Aqueous Medium
Pechal, Miroslav,Strasak, Milan
, p. 374 - 380 (2007/10/02)
The effects of temperature, structure and sulphuric acid concentration on the selectivity of the oxidation of aliphatic ketones (R1COR2) (1a-g) by thallic sulphate have been investigated.With increasing temperature the quantity of internal α-hydroxyketone (3a-d) decreases and the quantity of 1-hydroxyketone (2a-d) increases in the oxidation of methyl alkyl ketone (R2>CH3) (1a-d).The same concerns to the oxidation products of hexan-3-one (1e): 2-hydroxy-hexan-3-one (2e) and 4-hydroxy-hexan-3-one (3e), respectively. "The inverse selectivity temperature" (IST) for oxidation of linear methyl alkyl ketones (1a-c) and hexan-3-one (1e) has been found.With the use of the linear free-energy relationship it has been found that the selectivity of the reaction decreases with increasing the polar and steric effects of substituents R1,R2.With increasing the sulphuric acid concentration the selctivity of the oxidation of methyl alkyl ketones (1a, 1d) increases.
