반응 #93042

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acetic anhydride

pyridine

acetic anhydride

2-(4-Nitrobenzyloxycarbonylamino)-2-(3,4-dihydroxyphenyl) acetic acid

tetrahydrofuran

→

title acid

2-(4-Nitrobenzyloxycarbonylamino)-2-(3,4-diacetoxyphenyl)acetic acid

반응 조건

후처리

1. 1
   workup.ADDITIONwere added
2. 2
   기타to regain room temperature
3. 3
   기타The tetrahydrofuran was then removed by evaporation
4. 4
   기타the residue was partitioned between ethyl acetate and water
5. 5
   온도the pH raised to 7.5
6. 6
   기타The aqueous phase was separated
7. 7
   세척again washed with ethyl acetate
8. 8
   추출extracted with ethyl acetate (2×)
9. 9
   추출The total organic extract
10. 10
    세척was washed with water and brine
11. 11
    건조dried over sodium sulphate
12. 12
    기타evaporated
13. 13
    기타to give crude product
14. 14
    기타Reprecipitation
15. 15
    workup.ADDITIONby adding dropwise a solution of the crude material in dichloromethane to an excess of petrol

실험 절차

DL-2-(4-Nitrobenzyloxycarbonylamino)-2-(3,4-dihydroxyphenyl) acetic acid (1.81 g, 5 m mole) 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 (2×). 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.

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