Boc-L-phenylalanine methyl ester → (3S,4S)-4-(t-Butyloxycarbonylamino)-3-hydroxy-5-phenyl-1-pentene

Participants

Reaction Conditions

Reaction Steps

A solution of 10.25 g (36.7 mmol) Of N-(t-butyloxycarbonyl)phenylalanine methyl ester in 60 ml of toluene was cooled to -78° C. under inert atmosphere and treated dropwise over a period of 45 min with 35 ml (52.5 mmol) of diisobutylaluminum hydride in toluene. The resulting solution was stirred for 5 min, treated with 200 ml (200 mmol) of vinylmagnesium bromide, and allowed to warm to 0° C. for 16 h. The solution was subsequently quenched cautiously with methanol, treated with aqueous Rochelle salts, stirred for a few min, and filtered. The residue was digested several times with ethyl acetate and filtered; and the combined filtrates were washed with saturated brine, dried over MgSo4, and concentrated. Silica gel chromatography using 20% ethyl acetate in hexane gave 5.46 g (54%) of the desired compound (m.p. 98°-100° C., Rf 0.19, 3:1 hexane:ethyl acetate) along with 0.92 g (9%) of (3R,4S)-4-(t-butyloxycarbonylamino)-3-hydroxy-5-phenyl-1-pentene. 1H NMR (CDCl3) δ 1.39 (s, 9 H), 2.27 (br, 1 H), 2.90 (AA', 2 H), 3.80 (m, 1 H), 4.11 (m, 1 H), 4.79 (m, 1 H), 5.19 (dt, J=11, 1.5 Hz, 1 H), 5.28 (dt, J=18, 1.5 Hz, 1 H), 5.90 (ddd, J=18, 11, 6 Hz, 1 H), 7.15-7.35 (m, 5 H). Mass spectrum: (M+H)+ =2.76.

Provenance & Evidence