Methanol → tert-butyl (2S,3R)-3-hydroxy-1-phenylpent-4-en-2-ylcarbamate

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Reaction Steps

A solution of 3.03 g (11 mmol) of the resultant compound of Example 1 in 120 ml of 1:1 dichloromethane:methanol was cooled to 0° C., and treated with 4.10 g (11 mmol) of cerium(III) chloride heptahydrate. The resulting solution was immediately cooled to -78° and treated slowly with a solution of 0.63 g (16.5 mmol) of sodium borohydride in 15 ml of ethanol in such a way that the ethanolic solution was precooled by the side of the flask. After 1 h, the solution was quenched by addition of aqueous ammonium chloride, extracted with ether, washed sequentially with aqueous NaHCO3 and saturated brine, dried over MgSO4 and concentrated in vacuo to give a 4.7:1 ratio of diastereomeric products. Silica gel chromatography of the residue using 3:1 hexane:ethyl acetate provided 1.58 g (52%) of the pure desired compound (Rf 0.35, 15% ethyl acetate in chloroform) as a white solid (m.p. 122°-124° C.), along with 0.22 g (7%) of (3R,4S)-4-(t-butyloxycarbonylamino)-3-hydroxy-5-phenyl-1-pentene. 1H NMR (CDCl3) δ 1.37 (s, 9 H), 2.73 (dd, J=15, 9 Hz 1 H), 2.85 (dd J=15, 5 Hz, 1 H), 2.98 (m, 1 H), 3.98 (m, 1 H), 4.24 (m, 1 H), 4.58 (br, 1 H), 5.29 (dt, J=10, 1.5 Hz, 1 H), 5.38 (dt, J=17, 1.5 Hz, 1 H), 5.94 (ddd, J=17, 10, 6 Hz, 1 H), 7.2-7.3 (m, 5 H).

Provenance & Evidence