Process for the preparation of (3r,4r,5s)-4,5-epoxy-3-(1-ethylpropoxy)-1-cyclohexene-1-carboxylic acid ethyl ester
A technology of ethyl propoxy and ethyl formate, applied in the -4 field, can solve the problems of ring opening of epoxy products, benzene ring impurities, etc., and achieve the effect of reducing the cost of raw materials
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[0026] Example 1
[0027] (3R,4S,5R)-3,4,5-trihydroxy-1-cyclohexene-1-ethyl carboxylate
[0028] Shikimic acid (95% purity detected by HPLC) (100.0g, 0.55mol) was suspended in 400.0ml absolute ethanol at room temperature, and thionyl chloride (19.5ml, 0.27mol) was added dropwise with stirring. After dripping, heat to 78°C and reflux for 3 hours. After the reaction is complete, cool to 40°C and concentrate under reduced pressure to obtain a brown oil.
Example Embodiment
[0029] Example 2
[0030] Preparation of (3R, 4S, 5R)-3,4-O-isopentylidene-5-hydroxy-1-cyclohexene-1-carboxylic acid ethyl ester
[0031] Under nitrogen protection, add triethyl orthoformate (96.5ml, 0.57mol), 3-pentanone (61.5ml, 0.57mol), anhydrous ethanol (34.0ml, 0.57mol), benzenesulfonic acid (0.2g, 1.26mmol), stirred for 1 hour, and naturally heated to 45°C. In another reaction flask, add 100 ml of absolute ethanol to the brown oil obtained in Example 1, and stir evenly. The solution obtained above was added dropwise to the ethanol solution of (3R, 4S, 5R)-3,4,5-trihydroxy-1-cyclohexene-1-carboxylic acid ethyl ester, and stirring was continued for 2 hours. After the reaction was completed, it was concentrated to dryness under reduced pressure to obtain a dark brown oil. Add 500 ml of isopropyl acetate to dissolve the oil and wait for the next reaction.
Example Embodiment
[0032] Example 3
[0033] Preparation of (3R, 4S, 5R)-3,4-O-isopentylidene-5-O-(methylsulfonic acid)-1-cyclohexene-1-carboxylic acid ethyl ester
[0034] The isopropyl acetate solution of (3R, 4S, 5R)-3,4-O-isopentylidene-5-hydroxy-1-cyclohexene-1-carboxylate obtained in Example 2 was cooled to 0°C , Add methanesulfonyl chloride (56.8ml, 0.73mol), then add triethylamine (160.0ml, 1.15mol) dropwise, control the temperature not to exceed 10°C. After dripping, the temperature was naturally raised to room temperature, and stirring was continued for 30 minutes. Filter and wash the filter cake with 100 ml of isopropyl acetate. The filtrates were combined and washed with 300 ml of water. The separated isopropyl acetate layer was concentrated under reduced pressure to dryness to obtain a yellow oil.
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