Abstract
Chiral γ-lactones of both enantiomers were synthesized with more than 90% optical purities. The key step was Novozym 435–catalyzed hydrolysis of racemic N-benzyl-4-acetoxyalkylamides. Additionally, because (R)-γ-lactones are predominant in apricot, mango, peach, passion fruit, and strawberry, synthesis was attempted using only one enantiomer selectively. The (R)-enantimer was synthesized with more than 80% total yield and more than 90% optical purity by a combination of Novozym 435–catalyzed hydrolysis and the Mitsunobu reaction.
ACKNOWLEDGMENTS
We are grateful to Novozymes A/S for the generous gift of Novozym 435. Financial support from Meiji University (Grant-in-Aid for Young Scientists of Meiji University) is gratefully acknowledged.
Notes
a Substrate: 1.0 mmol, MeOH: 3.0 mmol, Novozym 435: 0.4 g, Pr2O: 20 ml, 60 °C.
b Determined by GC using Chirasil-Dex CB column.
c E =ln[1 − c (1 + eep)]/ln[1 − c (1 − eep)], where c = ees/(ees + eep), ees = enantiomeric excess of (R)-1, eep = enantiomeric excess of (S)-1.
a Substrate: 1.0 mmol, MeOH: 3.0 mmol, Novozym 435: 0.4 g, i Pr2O: 20 ml, 60 °C.
b Nucleophile: 1.0 mmol, PPh3: 1.0 mmol, DIAD: 1.0 mmol, solvent: 5 ml, rt.
c Total yield based on rac-2.
d Determined by GC using Chirasil-Dex CB column.