Method for synthesizing optical purity pine sawfly sex pheromone
A synthetic method, the technology of pine sawfly, which is applied in the field of synthesizing optically pure pine sawn bee sex pheromone, can solve the problems of cumbersome splitting, long routes, long reaction steps, etc.
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Embodiment 1
[0025] The synthesis of embodiment 1 (R)-5-bromo-4-methylpentanoic acid methyl ester (5a)
[0026]
[0027] In a 500mL three-necked bottle, dissolve 50g of the crude product lactone 4 in 200mL of anhydrous methanol. Pass dry HBr gas under stirring, and keep white mist in the bottle. After reacting at room temperature for 16 hours, it was detected by TLC that the raw material disappeared, and the flow of HBr gas was stopped. The solution was spin-dried under reduced pressure, the residue was extracted with ether (4×100mL), and the organic phase was washed with saturated NaHCO 3 Solution (2×80 mL), washed with saturated brine (2×50 mL), dried over anhydrous sodium sulfate, and spin-dried under reduced pressure. Distilled under reduced pressure, 28.54 g of compound 5a was collected as a 52°C-54°C / 60Pa fraction, with a weight yield of 56%. 2.16 (c1.1, CH 3 Cl) 1 H NMR (300MHz, CDCl 3 ): δ 3.68(s, 3H), 3.36-3.39(m, 2H), 2.35(t, 2H, J=7.5Hz), 1.75-1.90(m, 2H), 1.52-1.65(m, 1...
Embodiment 2
[0028] The synthesis of embodiment 2 (R)-5-bromo-4-methylpentanoic acid benzyl ester (5b)
[0029]
[0030] Dissolve 10 g of crude product lactone 4 in 100 mL of benzyl alcohol, pass dry HBr gas at room temperature until the raw material disappears, add diethyl ether to the residual solution, and distill the diethyl ether phase through saturated NaHCO 3 Solution (2×80 mL), washed with saturated brine (2×50 mL), dried over anhydrous sodium sulfate, and spin-dried under reduced pressure. Column chromatography separated to obtain 3.21 g of compound 5b, with a weight yield of 32.1%. 1 H NMR (300MHz, CDCl 3 ): δ 7.42-7.31 (m, 5H), 5.21 (s, 2H), 3.37-3.32 (m, 2H), 1.06 (d, 3H, J=6.9Hz); high-resolution mass spectrometry (HR-MS, MALDI) Calculated value C 13 h 17 o 2 BrNa: 307.0310; found 307.0314.
Embodiment 3
[0031] The synthesis of embodiment 3 (S)-4-methyl dodecanoic acid methyl ester (6a)
[0032]
[0033] Add 360mmg (15mmol) of magnesium chips into a 50mL three-necked bottle, fill it with nitrogen three times in vacuum, and then add 4mL of absolute anhydrous THF. Dissolve 1.79g (10mmol) of n-bromoheptane in 9mL of absolute anhydrous THF, first drop 10 drops, stir, after the reaction is triggered, continue to add dropwise, keep the reaction system slightly hot, continue to stir for 1 hour after the drop is completed, and let it stand Set aside.
[0034] Take another 50mL three-necked bottle, fill it with nitrogen three times under vacuum, add 0.672g (2.99mmol) of compound 5a, 5mL of absolute anhydrous THF, 0.1mL of 1.0M Li 2 CuCl 4 THF solution, 1.2 mL NMP. At room temperature, 3.6 mL (3.6 mmol) of the Grignard reagent prepared above was added dropwise. After reacting for 3 hours, it was detected by TLC that the reaction was complete. Add 20mL diethyl ether to dilute, th...
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