Hydrochloric Acid → tert-butyl 3-tert-butyl-L-tyrosinate

Participants

Reaction Steps

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.

Provenance & Evidence