反应详情

A suspension of 3.0 g (12 mmol) of (R)-α-(pivaloylmethyl)hydrocinnamic acid (see EPA 0.184.550) and 2.66 g (11 mmol) of L-histidine methyl ester dihydrochloride in 40 ml of dimethylformamide is treated at room temperature under a nitrogen atmosphere with 3.45 g (34 mmol) of triethylamine and 4.58 g (12 mmol) of HBTU. The reaction mixture is stirred at room temperature for 5 hours and subsequently evaporated in a high vacuum. The residue is dissolved in 500 ml of ethyl acetate and washed in succession with 100 ml of water, three times with 100 ml of saturated sodium bicarbonate solution each time and 100 ml of saturated sodium chloride solution. The organic phase is dried over sodium sulphate, evaporated under reduced pressure and the yellowish crude product obtained is chromatographed on silica gel with a 95:5 mixture of methylene chloride and methanol which contains 0.1% ammonia. In this manner there are obtained 3.6 g of N-[(R)-α-(3,3-dimethyl-2-oxobutyl)hydrocinnamoyl]-L-histidine methyl ester as a colourless foam, MS: 399 (M)+.

1. customsubsequently evaporated in a high vacuum
2. dissolutionThe residue is dissolved in 500 ml of ethyl acetate
3. washwashed in succession with 100 ml of water, three times with 100 ml of saturated sodium bicarbonate solution each time and 100 ml of saturated sodium chloride solution
4. dry with materialThe organic phase is dried over sodium sulphate
5. customevaporated under reduced pressure
6. customthe yellowish crude product obtained
7. customis chromatographed on silica gel with a 95:5 mixture of methylene chloride and methanol which