131029-01-1Relevant articles and documents
Chiral switch of enzymatic ketone reduction by addition of γ-cyclodextrin
Petkova, Galina A.,Král, Vladimír
, p. 6651 - 6656 (2010)
We report a chiral switch in the configuration of 1-(p-methoxyphenyl)- propan-2-ol, synthesized in aqueous media by ketoreductase in the presence of high concentration of γ-CD. NMR, ECD and fluorescence spectrometry were used in the effort to explain this
Chemoenzymatic synthesis of enantiomerically pure syn-configured 1-aryl-3-methylisochroman derivatives
Simon, Robert C.,Busto, Eduardo,Richter, Nina,Belaj, Ferdinand,Kroutil, Wolfgang
, p. 111 - 121 (2014)
A two-step synthesis of various enantiomerically pure 1-aryl-3- methylisochroman derivatives was accomplished through asymmetric biocatalytic ketone reduction followed by an oxa-Pictet-Spengler reaction. The compounds were obtained in good to excellent yield (47-92 %) in favor of the syn diastereomers [dr (syn/anti) up to 99:1]. Enantiopure arylpropanols serving as pronucleophiles for the C-C bond-formation step were obtained by biocatalytic reduction by employing enantiocomplementary alcohol dehydrogenases, which gave access to the (S) and (R) enantiomer with up to >99 % conversion and up to >99 % ee. A two-step sequence involving a biocatalytic hydrogen-transfer reduction and a syn-diastereoselective oxa-Pictet-Spengler reaction was established to provide a series of 1-aryl-3-methylchroman derivatives with perfect enantioselectivity; PTSA = para-toluenesulfonic acid. Copyright
Assignment of the absolute configurations of l-Aryl-2-propanols with the use of phosphoroselenoyl chlorides as chiral derivatizing agents
Murai, Toshiaki,Tsuji, Hiromi,Imaizumi, Satoko,Maruyama, Toshifumi
, p. 524 - 526 (2010)
Phosphoroselenoyl chloride bearing a l,1′-bi-2-naphthyl group was reacted with racemic 2-alkanols to give the corresponding esters. Based on the multiple combination of their NMR spectra, a method for the assignment of the absolute configuration of 1 -aryl-2-propanols was established. The solidstate conformations of the esters were confirmed by X-ray structure analyses.
Markovnikov Wacker-Tsuji Oxidation of Allyl(hetero)arenes and Application in a One-Pot Photo-Metal-Biocatalytic Approach to Enantioenriched Amines and Alcohols
Albarrán-Velo, Jesús,Gotor-Fernández, Vicente,Lavandera, Iván
supporting information, p. 4096 - 4108 (2021/08/19)
The Wacker-Tsuji aerobic oxidation of various allyl(hetero)arenes under photocatalytic conditions to form the corresponding methyl ketones is presented. By using a palladium complex [PdCl2(MeCN)2] and the photosensitizer [Acr-Mes]ClO4 in aqueous medium and at room temperature, and by simple irradiation with blue led light, the desired carbonyl compounds were synthesized with high conversions (>80%) and excellent selectivities (>90%). The key process was the transient formation of Pd nanoparticles that can activate oxygen, thus recycling the Pd(II) species necessary in the Wacker oxidative reaction. While light irradiation was strictly mandatory, the addition of the photocatalyst improved the reaction selectivity, due to the formation of the starting allyl(hetero)arene from some of the obtained by-products, thus entering back in the Wacker-Tsuji catalytic cycle. Once optimized, the oxidation reaction was combined in a one-pot two-step sequential protocol with an enzymatic transformation. Depending on the biocatalyst employed, i. e. an amine transaminase or an alcohol dehydrogenase, the corresponding (R)- and (S)-1-arylpropan-2-amines or 1-arylpropan-2-ols, respectively, could be synthesized in most cases with high yields (>70%) and in enantiopure form. Finally, an application of this photo-metal-biocatalytic strategy has been demonstrated in order to get access in a straightforward manner to selegiline, an anti-Parkinson drug. (Figure presented.).
Enantioselective Reduction of Ketones and Synthesis of 2-Methyl-2,3-dihydro-1-benzofuran Catalyzed by Chiral Spiroborate Ester
Chopade, A. U.,Chopade, M. U.,Nikalje, M. D.,Patil, H. S.
, p. 611 - 618 (2021/06/02)
Abstract: Asymmetric reduction of homobenzylic ketones was achieved through the use of chiral spiroborate ester catalyst. The catalyst is applicable for both analytical and industrial purposes since it is not sensitive to air and moisture. A rapid synthetic route has been developed for the preparation of (S)-2-methyl-2,3-dihydro-1-benzofuran via enantioselective reduction of homobenzylic ketone in the presence of a chiral spiroborate catalyst as the key step.
Fe-Catalyzed Anaerobic Mukaiyama-Type Hydration of Alkenes using Nitroarenes
Bhunia, Anup,Bergander, Klaus,Daniliuc, Constantin Gabriel,Studer, Armido
supporting information, p. 8313 - 8320 (2021/03/08)
Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama-type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe-catalyzed anaerobic Markovnikov-selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov-selectivity. The method features large functional group tolerance and is also applicable for late-stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
Hydroperoxidations of Alkenes using Cobalt Picolinate Catalysts
Peralta-Neel, Zulema,Woerpel
supporting information, p. 5002 - 5006 (2021/06/30)
Hydroperoxides were synthesized in one step from various alkenes using Co(pic)2as the catalyst with molecular oxygen and tetramethyldisiloxane (TMDSO). The hydration product could be obtained using a modified catalyst, Co(3-mepic)2, with molecular oxygen and phenylsilane. Formation of hydroperoxides occurred through a rapid Co-O bond metathesis of a peroxycobalt compound with isopropanol.
A General Regioselective Synthesis of Alcohols by Cobalt-Catalyzed Hydrogenation of Epoxides
Beller, Matthias,Junge, Kathrin,Leischner, Thomas,Li, Wu,Liu, Weiping
supporting information, p. 11321 - 11324 (2020/05/16)
A straightforward methodology for the synthesis of anti-Markovnikov-type alcohols is presented. By using a specific cobalt triphos complex in the presence of Zn(OTf)2 as an additive, the hydrogenation of epoxides proceeds with high yields and selectivities. The described protocol shows a broad substrate scope, including multi-substituted internal and terminal epoxides, as well as a good functional-group tolerance. Various natural-product derivatives, including steroids, terpenoids, and sesquiterpenoids, gave access to the corresponding alcohols in moderate-to-excellent yields.
Cobalt-Catalyzed Regioselective Olefin Isomerization under Kinetic Control
Liu, Xufang,Zhang, Wei,Wang, Yujie,Zhang, Ze-Xin,Jiao, Lei,Liu, Qiang
supporting information, p. 6873 - 6882 (2018/05/30)
Olefin isomerization is a significant transformation in organic synthesis, which provides a convenient synthetic route for internal olefins and remote functionalization processes. The selectivity of an olefin isomerization process is often thermodynamically controlled. Thus, to achieve selectivity under kinetic control is very challenging. Herein, we report a novel cobalt-catalyzed regioselective olefin isomerization reaction. By taking the advantage of fine-tunable NNP-pincer ligand structures, this catalytic system features high kinetic control of regioselectivity. This mild catalytic system enables the isomerization of 1,1-disubstituted olefins bearing a wide range of functional groups in excellent yields and regioselectivity. The synthetic utility of this transformation was highlighted by the highly selective preparation of a key intermediate for the total synthesis of minfiensine. Moreover, a new strategy was developed to realize the selective monoisomerization of 1-alkenes to 2-alkenes dictated by installing substituents on the γ-position of the double bonds. Mechanistic studies supported that the in situ generated Co-H species underwent migratory insertion of double bond/β-H elimination sequence to afford the isomerization product. The less hindered olefin products were always preferred in this cobalt-catalyzed olefin isomerization due to an effective ligand control of the regioselectivity for the β-H elimination step.
Methodology Development in Directed Evolution: Exploring Options when Applying Triple-Code Saturation Mutagenesis
Qu, Ge,Lonsdale, Richard,Yao, Peiyuan,Li, Guangyue,Liu, Beibei,Reetz, Manfred T.,Sun, Zhoutong
, p. 239 - 246 (2018/02/09)
Directed evolution of stereo- or regioselective enzymes as catalysts in asymmetric transformations is of particular interest in organic synthesis. Upon evolving these biocatalysts, screening is the bottleneck. To beat the numbers problem most effectively, methods and strategies for building “small but smart” mutant libraries have been developed. Herein, we compared two different strategies regarding the application of triple-code saturation mutagenesis (TCSM) at multiresidue sites of the Thermoanaerobacter brockii alcohol dehydrogenase by using distinct reduced amino-acid alphabets. By using the synthetically difficult-to-reduce prochiral ketone tetrahydrofuran-3-one as a substrate, highly R- and S-selective variants were obtained (92–99 % ee) with minimal screening. The origin of stereoselectivity was provided by molecular dynamics analyses, which is discussed in terms of the Bürgi–Dunitz trajectory.
