Triethylamine → N,N'-Dicyclohexylurea

Participants

Reaction Steps

For reaction by the active ester process, 14.6 g. (0.06 mol) N-(toluene-4-sulphonyl)-L-alanine and 12.2 g. (0.09 mol) N-hydroxybenzotriazole are dissolved in 300 ml. anhydrous ethyl acetate, cooled to 0° C. and mixed with 12.4 g. (0.06 mol) dicyclohexylcarbodiimide. For the formation of the active ester, the reaction mixture is stirred for 2 hours at 0° C. and then for a further 2 hours at ambient temperature. After the addition of 6.2 g. (0.04 mol) 3,5-dimethoxyphenol and 5.5 ml. (0.04 mol) triethylamine, the reaction mixture is stirred for 15 hours at ambient temperature. The N,N'-dicyclohexylurea formed is filtered off with suction and the filtrate is evaporated in a vacuum at a maximum bath temperature of 50° C. The residue is taken 200 ml. ethyl acetate and successively washed, in each case three times, with 100 ml. amounts of 5% citric acid and then with 100 ml. amounts of 5 % sodium bicarbonate solution. After drying with anhydrous sodium sulphate, the organic phase is evaporated in a vacuum. The oily crude product obtained is purified column chromatographically with a silica gel column, using tolueneethyl acetate (4:1 v/v) as elution agent. After evaporating the appropriately collected fractions, the residue is dissolved in a little methylene chloride and the product precipitated out by the addition of diethyl ether, there being obtained 5.8 g. (38% of theory) 1-[N-(toluene-4'-sulphonyl)-L-alanyloxy]3,5-dimethoxybenzene in the form of colorless crystals; m.p. 110° C.; αD20 : -52.5° (c=1% in acetone).

Provenance & Evidence