反应详情

The crude 6-hydroxy-piperidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-methyl ester, 36, obtained in the previous step is dissolved in methanol (500 mL) and treated with Dowex-50 (1.0 g). After stirring at rt for 3 hr, the solution is filtered and concentrated in vacuo, and the residue is purified over silica (hexanes/ethyl acetate, 5:1) to afford 2.1 g of the desired product. 1H NMR (CDCl3) δ 5.43 (br s, 0.5H), 5.28 (br s, 0.5H), 4.88 (br s, 0.5H), 4.66 (br s, 0.5H), 3.73 (s, 3H), 3.33 (s, 3H), 2.32 (m, 1H), 1.87 (m, 2H), 1.70–1.40 (m, 3H), 1.51 (s, 9H).

1. additiontreated with Dowex-50 (1.0 g)
2. filtrationthe solution is filtered
3. concentrationconcentrated in vacuo
4. customthe residue is purified over silica (hexanes/ethyl acetate, 5:1)