Chemo-enzymatic synthesis of key intermediates (S)-gamma-hydroxymethyl-alpha,beta- butenolide and (S)-gamma-hydroxymethyl-gamma-butyrolactone via lipase-mediated Baeyer-Villiger oxidation of levoglucosenone
Résumé
Levoglucosenone (LGO), a valuable chiral platform chemical that can be efficiently produced from catalytic fast pyrolysis of cellulose, has been efficiently converted into optically pure (S)-gamma-hydroxymethyl-alpha,beta-butenolide (HBO) using a two-step sequence involving a lipase-mediated Baeyer-Villiger oxidation and an acid hydrolysis. In the same fashion, (S)-gamma-hydroxymethyl-gamma-butyrolactone (2H-HBO) was successfully obtained through a three-step sequence (Baeyer-Villiger, palladium-catalysed hydrogenation and acid hydrolysis). The use of solid buffers in the lipase-mediated Baeyer-Villiger oxidation has proved beneficial in two ways: not only the reaction time and the enzymatic load were both reduced four-fold (from 8 to 2 hours and 464 to 113 U mmol(-1)) to reach conversions >= 83%, but solid buffers also prevented lipase from denaturation, thus preserving its enzymatic activity and allowing its use for further oxidation cycles.