TECHNOLOGICAL METHOD FOR SYNTHESIS OF OPTICALLY PURE L-/D-LACTIDE CATALYZED BY BIOGENIC GUANIDINE

摘要

A technological method for synthesizing optically pure L-/D-lactide by using a biogenic guanidine catalysis method. The method of the present invention comprises: by using biogenic guanidine creatinine (CR) as a catalyst and L-/D-lactic acid (90% of mass content) as a raw material, synthesizing optically pure L-/D-lactide by using a reactive reduced pressure distillation catalysis method. The method of the present invention has advantages that the used catalyst is biogenic guanidine creatinine and free of toxicity, metal, and cytotoxicity; the synthesized lactide is high in optical purity (the specific rotation of the L-lactide [α]25 D=−276˜−280, and the specific rotation of the D-lactide [α]25 D=280), and does not contain any metal; the amount of the catalyst used in reaction is low, the technological process is simplified (a process for rectifying and purifying a crude lactide product by using a conventional method is avoided); and the technological method is simple and convenient to operate and easy in industrial implementation.

主权项

1. A technological method for synthesizing optically pure L-/D-lactide by using biogenic guanidine catalysis method, wherein the optically pure L-/D-lactide is synthesized through the reactive reduced pressure distillation catalysis method using biogenic guanidine compound creatinine as a catalyst and L-/D-lactic acid (90% of mass content) as a raw material, comprising the following steps:
(1) Under the condition of heating temperature of 130° C.-170° C., L-/D-lactate was firstly reacted under normal pressure conditions for 1-4 h, then reacted 2-8 h under reduced pressure 30-60 torr, to produce lactic acid oligomers with the weight -average molecular weight of 600-1500 Da by dehydration and polycondensation; (2) The lactic acid oligomers synthesized in step (1) was added to catalyst creatinine to react 1-4 h with the controlled temperature at 150-260° C. and degree of vacuum at 2-15 torr, and then the distilled white crude L-/D-lactide was collected; (3) The crude L-/D-lactide collected in step (2) was washed using alkali with the mass concentration of 1-10%, then washed to neutral using the deionized water, vacuum dried at 20° C.-40° C. for 24-36 h to get the L-/D-lactide with high optical purity.