Minor enantiomer recycling: metal catalyst, organocatalyst and biocatalyst working in concert.
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.
Wingstrand
Erica
E
KTH School of Chemical Science and Engineering, Organic Chemistry, 100 44 Stockholm, Sweden.
Laurell
Anna
A
Fransson
Linda
L
Hult
Karl
K
Moberg
Christina
C
D055162:Biocatalysis; D005656:Fungal Proteins; D007700:Kinetics; D008049:Lipase / Q000378:metabolism; D008670:Metals / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D013237:Stereoisomerism
D005656:Fungal Proteins; D008670:Metals; D009930:Organic Chemicals; D008049:Lipase; C431349:lipase B, Candida antarctica