Sulfuric Acid → tert-butyl (2S)-2-amino-3-(4-hydroxy-3-iodophenyl)propanoate

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A mixture of 5.0 g of 3-iodo-L-tyrosine (Aldrich) and 2.5 mL of conc. H2SO4 in 85 mL of 1,4-dioxane was added to 30 mL of liquid isobutylene (condensed at −78° C.) in a 300 mL pressure bottle. The vessel was stoppered and the contents stirred at RT. After 3 days the bottle was cooled in an ice water bath, opened and the solution poured into a mixture of 10 g of NaHCO3 in 150 mL of water. The resulting mixture was subjected to rotary evaporation to remove isobutylene and dioxane. A white solid resulted which was collected by filtration and dried in vacuo. Analysis by tlc (SiO2, 95:5 CH2Cl2:MeOH) indicated major and minor components at Rf=0.52 and 0.60 respectively. The crude product was purified by flash chromatography on silica gel (95:5 CH2Cl2:MeOH) to afford 3.4 g (58%) of tert-butyl 3-iodo-L-tyrosinate as a white crystalline solid, m.p. 158-159° C.

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