反应详情

O-Benzyl-D-serine (5.0 g, 25.6 mmole) was dissolved in dimethylformamide (50 ml), treated with chlorotrimethylsilane (3.053 g, 28.1 mmole) and the mixture stirred at room temperature until a homogeneous solution was obtained (approx. 1 hour). Meanwhile, N-benzyloxycarbonyl-β-benzyl-L-aspartic acid (9.14 g, 25.6 mmole) was dissolved in a 1:1 mixture of dimethylformamide and tetrahydrofuran, cooled to -15° C. and treated with N-methylmorpholine (2.81 ml, 25.6 mmole), followed by isobutyl chloroformate (3.32 ml, 25.6 mmole). After 10 minutes' activation, the precooled solution of O-benzyl-D-serine silyl ester was added, followed by dropwise addition of N-methylmorpholine (2.81 ml, 25.6 mmole), ensuring that the temperature of the reaction mixture was maintained at -15° C. The solution was allowed to warm to room temperature slowly and stirred for 4 hours before acidifying to pH 1-2 (with cooling) using aqueous hydrochloric acid. Chloroform was added, the phases separated and the aqueous layer re-extracted with chloroform. The combined organic extracts were washed with 1N hydrochloric acid (3×) and with saturated sodium chloride and dried (MgSO4) The solvent was evaporated under reduced pressure and the solid residue crystallized from ethyl acetate/hexanes to give Nα -benzyloxycarbonyl-β-benzyl-L-aspartyl-O-benzyl-D-serine (11.0 g), m.p. 107°-108° C., which was homogeneous by TLC. The nmr spectrum of the product was consistent with the assigned structure.

1. customwas obtained (approx. 1 hour)
2. temperaturecooled to -15° C.
3. temperaturewas maintained at -15° C
4. temperatureto warm to room temperature slowly
5. stirringstirred for 4 hours
6. temperaturebefore acidifying to pH 1-2 (with cooling)
7. customthe phases separated
8. extractionthe aqueous layer re-extracted with chloroform
9. washThe combined organic extracts were washed with 1N hydrochloric acid (3×) and with saturated sodium chloride
10. dry with materialdried (MgSO4) The solvent
11. customwas evaporated under reduced pressure
12. customthe solid residue crystallized from ethyl acetate/hexanes