Optimisation of the Enantioselective Synthesis of Cyanohydrin Esters
作者:Lars Veum、Liisa T. Kanerva、Peter J. Halling、Thomas Maschmeyer、Ulf Hanefeld
DOI:10.1002/adsc.200505031
日期:2005.6
lipase-catalysed enantioselectivesynthesis of cyanohydrin esters was investigated, and the problem of previously reported low yields due to residual water in the reaction mixture was addressed. When the lipase was immobilised on Celite R-633 as a carrier, both the enantioselectivity and the reaction times for this dynamic kineticresolution were improved, thus enabling a highlyenantioselectivesynthesis of aromatic
Additions of structurally diverse α-ketonitriles to aromatic and aliphatic prochiral aldehydes yielding highly enantioenriched acylated cyanohydrins were achieved using a combination of a titanium salen dimer and an achiral or chiral Lewis base. In most cases high yields and high enantioselectivities were observed. The ee was moderate in the initial part of the reaction but increased over time. This
An Asymmetric, Chemo-Enzymatic Synthesis ofO-Acetylcyanohydrins
作者:Yuri N. Belokon、A. John Blacker、Lisa A. Clutterbuck、David Hogg、Michael North、Christopher Reeve
DOI:10.1002/ejoc.200600467
日期:2006.10
A one-pot chemo-enzymaticsynthesis of highly enantiomerically enriched O-acetylcyanohydrins has been developed. The bimetallic (salen)titanium complex 1 is used to convert aldehydes into nonracemic (R)-O-acetylcyanohydrins with 61 to 93 % enantiomeric excess. A lipase enzyme is then used to hydrolyse the unwanted (S) enantiomer of the product, leaving (R)-O-acetylcyanohydrins with 80 to >99 % enantiomeric