反应详情

203 ml 1.6M Butyllithium in hexane were added to a solution of 46.0 ml diisopropylamine in 120 ml THF at 0° over 1 h. The resultant LDA-solution was stirred at 0° for 1 h and then cooled down to −75°. 50.8 g 3-cyclopentyl-propionic acid methylester dissolved in 65 ml THF were added at −75° over 1 h and stirring at that temperature was continued for 1 h. 67.6 g 3-(3-tert-butoxy-2-oxo-propyl)-1,5,5-trimethyl-imidazolidine-2,4-dione dissolved in 65 ml THF were added at −75° over 1 h and after additional stirring at −75° for 1 h, 50 ml conc. H2SO4 were added over 15 minutes. The reaction mixture was refluxed for 3 h, cooled down to r.t. and hydrolyzed with 300 ml deionized water. The organic layer was separated, washed with 10% brine and dried over Na2SO4. Filtration and evaporation of the solvent afforded 96.5 g crude 3-(4-cyclopentylmethyl-3-hydroxy-5-oxo-tetrahydro-furan-3-ylmethyl)-(1,5,5-trimethyl-imidazolidine-2,4-dione as a yellow oil, which was used without purification for the next step. 3-Cyclopentyl-propionic acid methylester was prepared from the corresponding acid (ACROS No. 11161). The methylester is also available at Chemische Fabrik K. Bucher.

1. temperaturecooled down to −75°
2. additionwere added at −75° over 1 h
3. additionwere added at −75° over 1 h
4. stirringafter additional stirring at −75° for 1 h
5. temperatureThe reaction mixture was refluxed for 3 h
6. customThe organic layer was separated
7. washwashed with 10% brine
8. dry with materialdried over Na2SO4
9. filtrationFiltration and evaporation of the solvent