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Minor Enantiomer Recycling: Metal Catalyst, Organocatalyst and Biocatalyst Working in Concert
Author(s) -
Wingstrand Erica,
Laurell Anna,
Fransson Linda,
Hult Karl,
Moberg Christina
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901338
Subject(s) - candida rugosa , chemistry , lewis acids and bases , enantiomer , catalysis , lipase , candida antarctica , hydrolysis , organic chemistry , biocatalysis , lewis acid catalysis , enantiomeric excess , solvent , enantioselective synthesis , enzyme , reaction mechanism
A minor enantiomer recycling one‐pot procedure employing two reinforcing chiral catalysts has been developed. Continuous regeneration of the achiral starting material is effected via selective enzyme‐catalyzed hydrolysis of the minor product enantiomer from Lewis acid–Lewis base catalyzed addition of acyl cyanides to prochiral aldehydes in a two‐phase solvent system. The process provides O‐acylated cyanohydrins in close to perfect enantioselectivities, higher than those obtained in the direct process, and in high yields. A combination of a ( S , S )‐salen Ti Lewis acid and Candida antarctica lipase B provides the products with R absolute configuration, whereas the opposite enantiomer is obtained from the ( R , R )‐salen Ti complex and Candida rugosa lipase.