反应详情

温度

0 °C

DL-2-(4-Nitrobenzyloxycarbonylamino)-2-(3,4-dihydroxyphenyl)acetic acid (1.81 g, 5 mmole) was dissolved in dry tetrahydrofuran (19 ml). The solution was cooled to 0° C. and stirred while dry pyridine (1.30 ml, 3 equivalents) and acetic anhydride (1.18 ml, 2.5 equivalents) were added. The solution was allowed to regain room temperature and stirred for 3 h, further acetic anhydride (0.5 ml) being added after 1 h. The tetrahydrofuran was then removed by evaporation, the residue was partitioned between ethyl acetate and water and the pH raised to 7.5. The aqueous phase was separated and again washed with ethyl acetate, the organic phases being discarded, then acidified to pH2 with 2M hydrochloric acid and extracted with ethyl acetate (2X). The total organic extract was washed with water and brine, then dried over sodium sulphate and evaporated to give crude product. Reprecipitation was effected by adding dropwise a solution of the crude material in dichloromethane to an excess of petrol, with vigorous stirring, to give the title acid as an amorphous powder which was filtered, washed with petrol and dried; it retained solvents tenaciously (1.46 g, 65%); δ(CDCl3) 8.24 and 8.26 (6H,2s,2×CH3CO), 5.15(2H,s,ArCH2O), 5.22 (1H,d,J 7 Hz, NCHCO) 7.0-7.6 (7H,m,5H on D2O exch, aryl-H+NH+OH), 8.13(2H,d,J 9 Hz, aryl-H); RF 0.50 in chloroform:methanol:acetic acid, 17:2:1;

1. additionwere added
2. customto regain room temperature
3. customThe tetrahydrofuran was then removed by evaporation
4. customthe residue was partitioned between ethyl acetate and water
5. temperaturethe pH raised to 7.5
6. customThe aqueous phase was separated
7. washagain washed with ethyl acetate
8. extractionextracted with ethyl acetate (2X)
9. extractionThe total organic extract
10. washwas washed with water and brine
11. dry with materialdried over sodium sulphate
12. customevaporated
13. customto give crude product
14. customReprecipitation
15. additionby adding dropwise a solution of the crude material in dichloromethane to an excess of petrol