394735-17-2

Example-1: Preparation of ethyl 2-amino-3-cyclobutylpropionate (formula-4a) Ethyl 2-(diphenylmethyleneamino) acetate (Formula-A3, 250 g) was dissolved in tetrahydrofuran (2000 mL) and the mixture was cooled to 0-5°C. Potassium tert-butoxide (157.4 g) was slowly added at a temperature below 10°C and stirred at 0-5°C for 1 hour. Subsequently, bromomethylcyclobutane (185 g) was slowly added over 30 minutes at 0-5 °C. The reaction mixture was warmed to 25-30 °C and stirring was continued for 30 hours. After completion of the reaction, 2N hydrochloric acid was added to the reaction mixture and stirred for 6 hours. Dichloromethane was added and after stirring for 15 minutes, the organic and aqueous layers were separated. The aqueous layer was washed with dichloromethane. Dichloromethane was added to the aqueous layer and cooled to 0-5°C. The pH of the reaction mixture was adjusted to 12.5 with 50% sodium hydroxide solution, stirred for 10 minutes and the organic and aqueous layers were separated again. The aqueous layer was extracted with dichloromethane at 0-5°C. All organic layers were combined, dried with anhydrous sodium sulfate and the solvent was removed by distillation under reduced pressure to give the target product ethyl 2-amino-3-cyclobutylpropionate. Yield: 45 g.

[1] Letters in Organic Chemistry, 2016, vol. 13, # 5, p. 352 - 358
[2] Patent: WO2005/85197, 2005, A1. Location in patent: Page/Page column 58-59
[3] Patent: US2006/276407, 2006, A1. Location in patent: Page/Page column 410
[4] Patent: US2006/281688, 2006, A1. Location in patent: Page/Page column 622
[5] Patent: WO2014/61034, 2014, A1. Location in patent: Page/Page column 9; 27; 35