反应详情

A solution of ethyl 2-(benzyloxycarbonylamino)-2-(piperidin-1-ylmethyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)hexanoate (0.26 g, 0.51 mmol) in 6 N HCl (20 mL) was heated to a gentle reflux for 48 h. After cooling to room temperature, the solution was washed with dichloromethane (5×15 mL) and concentrated (aqueous layer). The resulting residue was dissolved in water (3 mL) and passed through cation exchange resin Dowex 50-200 eluted with 2 N ammonia (4 g resin was loaded on a column, washed successively with water, 1 N HCl, water to neutral pH, 2 N ammonia solution and water to neutral pH). Fractions containing product were concentrated, diluted with minimal water, acidified with 6 N HCl, frozen and lyophilized to give 2-amino-6-borono-2-(piperidin-1-ylmethyl)hexanoic acid dihydrochloride. (60 mg, 43%). 1H NMR (D2O) δ 3.64-3.53 (m, 1H), 3.34 (d, J=13.9 Hz, 1H), 3.05-3.03 (m, 2H), 2.93-2.91 (m, 3H), 1.76-1.67 (m, 5H), 1.53-1.46 (m, 3H), 1.31-1.30 (m, 3H), 1.09-1.07 (m, 1H), 0.70 (t, J=7.3 Hz, 2H). MS found for C12H25BN2O4 m/z[254(M−18+1)].

1. temperaturea gentle reflux for 48 h
2. washthe solution was washed with dichloromethane (5×15 mL)
3. concentrationconcentrated (aqueous layer)
4. dissolutionThe resulting residue was dissolved in water (3 mL)
5. washeluted with 2 N ammonia (4 g resin
6. washwashed successively with water, 1 N HCl, water to neutral pH, 2 N ammonia solution and water to neutral pH)
7. additionFractions containing product
8. concentrationwere concentrated
9. additiondiluted with minimal water
10. temperaturefrozen