Hydrochloric Acid → Boc-O-ethyl-L-tyrosine

Participants

Reaction Steps

N-t-butoxycarbonyl-L-tyrosine (II, EXAMPLE 1, (235 g, 835 mmol) is dissolved in sodium hydroxide (4N, 705 mL) at 20-25°. Diethyl sulfate (210 mL, 1.60 mol) is added over 15-20 min. The reaction mixture is stirred for 2 hr, then it is cooled with ice-bath (internal temperature around 15°). Ethyl acetate (1400 mL) is added, followed by slow addition of hydrochloric acid (3N, 1410 mL) for 1 hr. The ethyl acetate layer is separated, and the aqueous layer is extracted with ethyl acetate (1400 mL). The ethyl acetate phase is concentrated to about 200 mL, then hexane (1600 mL) is added. The mixture is stirred in an ice-bath for 2 hr, filtered, washed with hexane (800 mL) in 3 portions. The precipitate is dried to give the title compound. The filtrate is concentrated, suspended in ethyl acetate/hexane (80/450 mL) for 2 hr, filtered and washed with hexane (250 mL) in 3 portions and dried to give additional title compound, NMR (MeOH-d4) δ7.11, 6.80, 4.22, 4.05, 3.08, 2.86 and 1.36; CMR δ175.4, 159.3, 157.8, 131.3, 130.4, 115.4, 80.5, 64.4, 56.4, 37.9, 28.7 and 15.2.

Provenance & Evidence