3-(Hydroxy(phenyl)methyl)azetidin-2-ones obtained via catalytic asymmetric hydrogenation or by biotransformation
摘要:
The catalytic asymmetric reduction of ethyl-2-(benzamidomethyl)-3-oxo-phenylpropanoate was realized with high enantiomeric and diastereoisomeric excesses via biotransformation using whole cells of different yeasts and asymmetric hydrogenation with Ru(II) complexes prepared from different chiral diphosphine ligands.With these combined approaches it was possible to prepare both enantiomers of the syn-stereoisomers in almost enantiomerically pure form; one of the enantiomers of the anti-stereoisomer was obtained in high ee with selected yeast while the other enantiomer of the anti was prepared in low ee and de. With three of the four epimers we were able to prepare the corresponding azetidinones. (C) 2011 Elsevier Ltd. All rights reserved.
Aqua iridium(III) complexes with 8-amino-5,6,7,8-tetrahydroquinolines CAMPY L1 and its derivatives as chiral ligands proved to be very efficient catalysts for the reduction of a wide range of prochiral aryl ketones, revealing a variety of behaviours in terms of reaction rate and stereoselectivity. As standard substrates, differently substituted acetophenones were studied and good enantioselectivity (86% ee) was achieved in the reduction of 1-(o-tolyl)ethan-1-one 6. Particularly interesting was the ATH reaction in the case of beta-amino keto esters, precursors of beta-lactams and azetidinones. The best results were obtained with [Cp*Ir(H2O)(L1)]SO4 affording the corresponding diastereomeric alcohols in an (R,S)-configuration with an excellent 99% ee in the reduction of 2-(benzamido methyl)-3-oxo-3-(4-(trifluoromethyl)phenyl) propanoate 12. (C) 2014 Elsevier Ltd. All rights reserved.
Iridium‐Catalyzed Enantioselective and Diastereoselective Hydrogenation of Racemic
<i>β’</i>
‐Keto‐
<i>β</i>
‐Amino Esters via Dynamic Kinetic Resolution
An iridium/f-diaphos catalytic system for the enantioselectivehydrogenation of α-substituted β-ketoesters via dynamic kinetic resolution is reported. The desired anti β’-hydroxy-β-amino esters were obtained in moderate to good yields (60–95%) with 72–99% ees and 91:9 to 99:1 drs. This protocol tolerates various functional groups and could be easily conducted on gram scale with lower catalyst loading
The catalytic asymmetric reduction of ethyl-2-(benzamidomethyl)-3-oxo-phenylpropanoate was realized with high enantiomeric and diastereoisomeric excesses via biotransformation using whole cells of different yeasts and asymmetric hydrogenation with Ru(II) complexes prepared from different chiral diphosphine ligands.With these combined approaches it was possible to prepare both enantiomers of the syn-stereoisomers in almost enantiomerically pure form; one of the enantiomers of the anti-stereoisomer was obtained in high ee with selected yeast while the other enantiomer of the anti was prepared in low ee and de. With three of the four epimers we were able to prepare the corresponding azetidinones. (C) 2011 Elsevier Ltd. All rights reserved.