- A facile one-pot synthesis of vinpocetine
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A one-pot synthesis of vinpocetine from vincamine was established. Lewis acids caused transesterification and/or dehydration of vincamine in EtOH. FeCl3 catalyzed both transesterification and dehydration while Ti(OEt)4 selectively catalyzed transesterification.
- Kuge,Nakazawa,Kometani,Sugaya,Mochida,Tomioka
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- A CHANGCHUN amine ethyl ester preparation method
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The invention discloses a preparation method of vincamine ethyl ester which is applied to the preparation field of a compound vinpocetine intermediate and impurities. The preparation method comprises the following steps: (1) in the presence of a first organic solvent and alkaline, enabling vincamine acid and an ethylation reagent to carry out ethylation reaction to obtain a reaction liquid, wherein the first organic solvent, the alkaline, the vincamine acid and the ethylation reagent are added into a reaction system by one step; (2) evaporating out the solvent from the reaction liquid obtained in the step (1) and then adding water to dissolve, washing an organic phase with a saline liquid after directly extracting by use of a second organic solvent to obtain an organic phase extracting liquid; (3) after dehydrating the organic phase extracting liquid obtained in the step (2) by a drying agent, filtering and concentrating to obtain a concentrated liquid; and (4) adding a third organic solvent into the concentrated liquid obtained in the step (3), separating out solids, filtering and drying the solids to obtain the vincamine ethyl ester. According to the preparation method of the vincamine ethyl ester, the raw materials are easily available and convenient to store, the reaction process is simple and convenient in operation, the safety is high, the cost is low, the yield of the vincamine ethyl ester is high, the quality of the vincamine ethyl ester is good, and needed reaction solvent and after-treatment solvent are little, and thus, the preparation method is suitable for the industrial production.
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Paragraph 0026-0033
(2017/05/20)
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- Kinetics and mechanisms of vinpocetine degradation in aqueous solutions
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Under stressed conditions, vinpocetine (1; ethyl apovincamin-22-oate) equilibrates with vincaminic acid ethyl ester (2) and 14-epivincaminic acid ethyl ester (3), and hydrolyzes to apovincaminic acid (4). Sequentially, 2 is equilibrated with 14-epivincaminic acid ethyl ester (3) and hydrolyzes to vincaminic acid (5), which equilibrates with 4 and 14-epivincaminic acid (6). At acidic pH, the major route of degradation is 1?2→5. However, at neutral pH, the major route of degradation is 1→4?5. The kinetics for the degradation of 1 in the pH 1-3 region is represented by a consecutive reaction with a reversible step (second-order), but the degradation of 1 in the pH 3.5-6.0 region follows pseudo first-order kinetics. Significant buffer catalysis is observed with acetate and phosphate buffers. Reactions are dependent on the ionic strength, pH, and temperature. No oxygen effect on the degradation of vinpocetine is found.
- Muhammad,Adams,Lee
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p. 126 - 131
(2007/10/02)
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- Process for the preparation of vincaminic acid esters
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The invention relates to a new process for the preparation of apovincaminic acid esters. More particularly, the invention concerns a process for preparing racemic and optionally active vincaminic acid esters of the formula (I) STR1 in which R1 and R2 independently stand for alkyl having from one to 6 carbon atoms, and 14-epimers thereof. According to the invention an octahydroindolo[2,3-a]quinolizine-oxime ester of the formula (II) STR2 in which R1 and R2 have the same meaning as defined above, is reacted with an aqueous solution of sulfurous acid or a salt thereof at a temperature of 80° to 110° C. and the 14-epimeric mixture obtained is epimerized or separated in a known manner and if desired, the racemic vincaminic acid esters are resolved. The valuable, pharmaceutically active compounds of the formula (I) can be prepared according to the invention in a considerably improved yield and the undesired side reactions can be suppressed and/or the by-products can easily be converted into other pharmaceutically active materials.
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