Synthesis
The general procedure for the synthesis of L-(+)-2-cyclohexylglycine from L-phenylglycine is as follows: the selective hydrogenation of optically active phenyl amino acids is carried out in a 100 ml stainless steel autoclave equipped with a magnetic stirring device. Prior to the addition of catalyst, the autoclave is purged three times with hydrogen gas to remove air completely. Under the protection of inert atmosphere, a suspension of freshly prepared nanoruthenium(at)lithium montmorillonite catalyst (containing 0.01592 mmol Ru, dissolved in 10 ml of H2O) was carefully transferred to the autoclave together with an appropriate amount of substrate, and then the autoclave was charged with hydrogen gas to a set pressure. The autoclave was placed in a preheated heating jacket, magnetic stirring was activated, and the reaction lasted for the specified time. At the end of the reaction, the autoclave was allowed to cool to room temperature and the internal pressure was slowly released. Thoroughly rinse the inside of the reactor with 2N NaOH solution to recover the products (if the reaction system is acidic, switch to 2N HCl solution). All collected solutions were filtered through a 0.22 μm PTFE membrane to remove the catalyst residue, followed by adjusting the pH of the filtrate with dilute HCl (or NaOH) solution to 5.5, at which point the products partially precipitated. The suspension was concentrated to 10 ml under vacuum to induce complete precipitation of the product. The precipitate was collected by filtration, washed with distilled water and finally dried under vacuum for 24 hours.
References
[1] Organic Process Research and Development, 2003, vol. 7, # 2, p. 164 - 167
[2] Journal of Organometallic Chemistry, 2016, vol. 812, p. 81 - 86
[3] Synthetic Communications, 1999, vol. 29, # 24, p. 4327 - 4332
[4] Journal of Medicinal Chemistry, 1993, vol. 36, # 1, p. 166 - 172
