Triphenylphosphine → 2-tert-Butoxycarbonylamino-2-(2-oxo-ethyl)-6-(4,4,5,5-tetramethyl-[1,3,2]-dioxaborolan-2-yl)-hexanoic acid ethyl ester

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Reaction Steps

A solution of Ethyl-2-allyl-2-(tert-butoxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)hexanoate (650 mg, 1.53 mmol) in dichloromethane (30 mL,) was cooled to −78° C. and treated with ozone until a pale blue-gray color appeared. After TLC indicated the absence of starting material, the ozone inlet tube was replaced with nitrogen and nitrogen was bubbled through the solution for 20 min to remove any excess ozone. Triphenylphosphine (1.20 g, 4.59 mmol, 3 equiv) was added in one portion, the cooling bath was removed and the mixture was stirred for 4 h. The solution was concentrated and purified by MPLC (0-40% ethyl acetate in heptane) gave the title compound as a colorless oil (608 mg, 93%). Rf 0.25 (30% ethyl acetate in heptane); 1H NMR (CDCl3, 300 MHz): δ 9.64 (s, CHO, 1H), 5.60 (br, s, NH, 1H), 4.19 (q, J=7.5 Hz, 2H), 3.56 (d, J=17 Hz, 1H), 2.93 (d, J=17.5 Hz, 1H), 2.20 (m, 1H), 1.62 (m, 1H), 1.38 (s, 9H), 1.28-1.43 (m, 4H), 1.23 (t, J=7 Hz, 3H), 1.21 (s, 12H) and 0.72 (t, J=7.5 Hz, 2H).

Provenance & Evidence