- Efficient asymmetric hydrogenation of pyridines
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Up to four stereocenters can be created efficiently in a single step by the asymmetric hydrogenation of oxazolidinone-substituted pyridines (see scheme). Furthermore, selective chirality transfer and nondestructive cleavage of the chiral auxiliary occur under the same reaction conditions, making an additional cleavage step unnecessary.
- Glorius, Frank,Spielkamp, Nick,Holle, Sigrid,Goddard, Richard,Lehmann, Christian W.
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- Acylative kinetic resolution of racemic methyl-substituted cyclic alkylamines with 2,5-dioxopyrrolidin-1-yl (: R)-2-phenoxypropanoate
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The diastereoselective acylation of a number of racemic methyl-substituted cyclic alkylamines with active esters of 2-phenoxypropanoic acid was studied in detail. The ester of (R)-2-phenoxypropanoic acid and N-hydroxysuccinimide was found to be the most selective agent. The highest stereoselectivity was observed in the kinetic resolution of racemic 2-methylpiperidine in toluene at -40 °C (selectivity factor s = 73) with the predominant formation of (R,R)-amide (93.7% de). To explain the observed stereoselectivity, DFT modelling of the transition states in the reactions of the title acylating agent with 2-methylpiperidine and 2-methylpyrrolidine was performed. The calculated values were in good agreement with experimental data. It has been demonstrated that the acylation proceeds via a concerted mechanism, in which the addition of an amine occurs simultaneously with the elimination of the hydroxysuccinimide fragment. The high stereoselectivity of the (R,R)-amide formation is largely ensured by the lower steric hindrances in the transition states as compared to the formation of (R,S)-amide.
- Bartashevich, Ekaterina V.,Chulakov, Evgeny N.,Ezhikova, Marina A.,Gruzdev, Dmitry A.,Kodess, Mikhail I.,Korolyova, Marina A.,Krasnov, Victor P.,Levit, Galina L.,Tumashov, Andrey A.,Vakarov, Sergey A.
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supporting information
p. 862 - 869
(2022/02/03)
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- Synthesis of: N -heterocycles from diamines via H2-driven NADPH recycling in the presence of O2
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Herein, we report an enzymatic cascade involving an oxidase, an imine reductase and a hydrogenase for the H2-driven synthesis of N-heterocycles. Variants of putrescine oxidase from Rhodococcus erythropolis with improved activity were identified. Substituted pyrrolidines and piperidines were obtained with up to 97% product formation in a one-pot reaction directly from the corresponding diamine substrates. The formation of up to 93% ee gave insights into the specificity and selectivity of the putrescine oxidase.
- Al-Shameri, Ammar,Borlinghaus, Niels,Weinmann, Leonie,Scheller, Philipp N.,Nestl, Bettina M.,Lauterbach, Lars
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p. 1396 - 1400
(2019/03/26)
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- First Direct Synthesis of Optically Active 3-Methylcyclopentene
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(-)-(S)- and (+)-(R)-3-methylcyclopentene (1) has been prepared in a stereochemically unambiguous synthesis.The (S)-configuration for (-)-1 was confirmed by correlation with (-)-(S)-1-methylindane.
- Sliwka, Hans-Richard,Hansen, Hans-Juergen
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p. 434 - 440
(2007/10/02)
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