Preparation method for natural product (-)-kainic acid
A technology of kainate oxalic acid and synthetic method, which is applied in the direction of organic chemical method, chemical instrument and method, bulk chemical production, etc., can solve the problems of low selectivity, high price, long route, etc., and achieve simple operation and low substrate Simple, short route effect
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Embodiment 1
[0035] Synthesis of (4S)-1-tert-butoxycarbonyl-3-(2-tert-butyl acetate)-2-pyrrolidone 2
[0036] Add the catalyst [Rh(OH)(L)] to the reaction flask 2(3.8mg, 0.01mmol), compound 1 (36.6mg, 0.2mmol), potassium isopropenyl fluoroborate (59.2mg, 0.4mmol), added toluene (2ml) under Ar gas protection, water (0.2ml), triethyl Amine (0.056ml), stirred at room temperature. After reacting for 24h, add ethyl acetate and extract three times. The organic phase was dried over anhydrous sodium sulfate. The organic phase was spin-dried and separated by column chromatography (eluent: petroleum ether / ethyl acetate=8 / 1) to obtain a white solid 2 (37 mg), with a yield of 82%.
[0037]
[0038] The characterization data of the obtained compound 2 are as follows:
[0039] [α] D 27 =+7.0 (c 0.95, CHCl 3 ), the ee value is 99%. 1 H NMR (400MHz, CDCl 3 ): δ1.51(s, 9H), 1.74(s, 3H), 2.46(dd, 1H, J=17.2, 9.6Hz), 2.60(dd, 1H, J=17.2, 8.0Hz), 2.86-2.95( m, 1H), 3.49(dd, 1H, J=10.8, 8.4Hz), 3....
Embodiment 2
[0041] Synthesis of (3R,4S)-1-tert-butoxycarbonyl-3-(2-tert-butyl acetate)-4-(2-propenyl)-2-pyrrolidone 3
[0042] Compound 2 (675mg, 3mmol) was added to the reaction flask, tetrahydrofuran (30ml) was added under the protection of Ar gas, and bis(trimethylsilylamide)lithium (1.0M in tetrahydrofuran) was slowly added dropwise at -78°C ( 4.5ml, 4.5mmol). After keeping the reaction at low temperature for 1 h, tert-butyl bromoacetate (0.67ml, 4.5mmol) was added dropwise. After reacting for 3 h, it was quenched by adding saturated ammonium chloride aqueous solution, extracted three times with ethyl acetate, and the organic phase was dried over anhydrous sodium sulfate. The organic phase was spin-dried and separated by column chromatography (eluent: petroleum ether / ethyl acetate=12 / 1) to obtain a white solid 3 (925 mg, 2.73 mmol), with a yield of 91%.
[0043] The characterization data of the obtained compound 3 are as follows:
[0044] [α] D 27 =+8.9 (c 1.00, CHCl 3 ). 1 H N...
Embodiment 3
[0046] Synthesis of (3S, 4S)-1-tert-butoxycarbonyl-3-(2-tert-butyl acetate)-4-(2-propenyl)-2-pyrrolidone 4
[0047] Take compound 3 (338mg, 1mmol) and add it to the reaction flask, add tetrahydrofuran (10ml) under the protection of Ar gas, slowly drop lithium bistrimethylsilylamide (1.0M in tetrahydrofuran) (1.5ml , 1.5mmol). After keeping the reaction at low temperature for 1 h, a solution of (L)-(-)-camphorsulfonic acid (464 mg, 2 mmol) in -78 °C tetrahydrofuran (10 ml) was quickly added. After reacting for 30 minutes, it was quenched by adding saturated ammonium chloride aqueous solution, extracted three times with ethyl acetate, and the organic phase was dried over anhydrous sodium sulfate. The organic phase was spin-dried and separated by column chromatography (eluent: petroleum ether / ethyl acetate=15 / 1) to obtain a white solid 4 (286 mg), with a yield of 84%.
[0048] The characterization data of the obtained compound 4 are as follows:
[0049] [α] D 27 =+20.3 (c 0....
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