反应详情

A stirred mixture of 12.8 g (0.049 mole) of N-carbobenzyloxy-4-keto-L-proline, 53 ml (0.095 mole) of ethylene glycol, and 0.35 g of p-toluenesulfonic acid H2O in 1.31 l. of benzene is heated and the resulting solution is refluxed for 7 hours (water formed is collected in a Dean-Stark apparatus). After standing overnight at room temperature, the lower glycol layer is separated and the benzene solution is washed with 150 ml of saturated sodium chloride, dried (MgSO4), and the solvent evaporated to give 14.6 g of N-carbobenzyloxy-4,4-ethylenedioxy-L-proline as a syrupy residue. The latter is dissolved in 60 ml of ethanol, filtered, treated with 5 g of cyclohexylamine, and diluted with ether. On seeding and rubbing, the crystalline cyclohexylamine salt separates; weight after cooling overnight, 9.0 g., m.p. 179°-180° (s. 173°). The material is recrystallized from acetonitrile, m.p. 182°-184° (s. 179°), [α]D26 -21° (c, 1 % in EtOh).

1. customformed
2. customis collected in a Dean-Stark apparatus)
3. customthe lower glycol layer is separated
4. washthe benzene solution is washed with 150 ml of saturated sodium chloride
5. dry with materialdried (MgSO4)
6. customthe solvent evaporated