Hydrochloric Acid → 3-Cyclohexyl-L-alanine

Participants

Reaction Conditions

Reaction Steps

20 g (121 mmol) L-phenylalanine are dissolved or suspended in 200 ml deionised water, 200 ml isopropanol and 12.2 ml (146 mmol) 37% hydrochloric acid. After addition of 2 g of the Pt/Rh catalyst, 4% Pt+1% Rh on activated carbon (water content approx. 50%, corresponding to approx. 5 wt. % catalyst relative to L-phenylalanine used), the reaction mixture is introduced into a 1 l hydrogenation autoclave. After being rendered inert with nitrogen three times, it is rinsed with hydrogen twice, then a hydrogen overpressure of 8-10 bar is established and the reaction solution heated to 50-60° C. After approximately 6 to 8 hours, hydrogen uptake is completed (theoretical amount of H2 8.1 l). The hydrogenator is depressurised and once again rendered inert with nitrogen three times. The still hot reaction solution is extracted with a nutsch filter and the catalyst is washed with 50 ml deionised water. The filtrate is first concentrated to low volume in vacuo (the isopropanol largely removed), the residue then adjusted to a pH of 5-6 with 50% sodium hydroxide solution. It is cooled to a temperature of 0-10° C., the product is extracted with a nutsch filter, rinsed with 50 ml deionised water and dried in a drying oven in vacuo at 50-70° C.

Provenance & Evidence