反应详情

To a 250 mL round bottomed flask equipped with a magnetic stirrer were added 30 mL of isobutylene (condensed at −78° C.), 1.30 g of 3-tert-butyl-L-tyrosine.HCl, 60 mL of 1,4-dioxane, and 0.5 mL of concentrated H2SO2. The flask was sealed with a rubber septum and wired shut. After stirring at RT for 18 h, the flask was vented and the contents poured into a solution of 10 g of NaHCO3 in 150 mL of water. The mixture was subjected to rotary evaporation to remove isobutylene. An emulsion resulted which was extracted with EtOAc (4×40 mL). The combined extracts were washed with 5% aqueous NaHCO3 (3×50 mL), dried over anhydrous MgSO4, and concentrated to give a light yellow foam. Analysis of the product by tlc (SiO2, 95:5 CH2Cl2:MeOH) indicated major and minor components at Rf=0.45 and 0.49 respectively. The Rf=0.45 product was isolated by flash chromatography on silica gel (95:5 CH2Cl2:MeOH) to afford 0.61 g (44%) of tert-butyl 3-tert-butyl-L-tyrosinate as a white foam, m.p. 43-52° C.

1. customTo a 250 mL round bottomed flask equipped with a magnetic stirrer
2. customThe flask was sealed with a rubber septum
3. customThe mixture was subjected to rotary evaporation
4. customto remove isobutylene
5. customAn emulsion resulted which
6. extractionwas extracted with EtOAc (4×40 mL)
7. washThe combined extracts were washed with 5% aqueous NaHCO3 (3×50 mL)
8. dry with materialdried over anhydrous MgSO4
9. concentrationconcentrated
10. customto give a light yellow foam
11. customThe Rf=0.45 product was isolated by flash chromatography on silica gel (95:5 CH2Cl2:MeOH)