Dimethylamine → (2R)-2-(2,4-difluorophenyl)-2-[(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-isobutyl-2,5-dioxopiperazin-1-yl]-N,N-dimethylethanamide

Beteiligte Stoffe

Reaktionsschritte

Carbonyldiimidazole (4.80 g, 1.54 equiv.) was suspended in anhydrous dichloromethane (40 mL) and the suspension was left at room temperature for 15 minutes. (2RS)-2-(2,4-difluorophenyl)-2-[(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-isobutyl-2,5-dioxopiperazin-1-yl]-N-(2-hydroxyphenyl)ethanamide (10.50 g, pre-dried in vacuo over P4O10 for 24 hours) was then added with stirring and the resultant solution was stirred at room temperature for 6 hours. The resulting yellow solution was then treated with a 2.0M solution of dimethylamine in tetrahydrofuran (54 mL, 5.6 equiv.) and the resulting mixture was stirred at room temperature for 16 hours. The solvents plus residual dimethylamine were removed under reduced pressure and the reaction mixture was taken up in dichloromethane (200 mL) and washed with 1M hydrochloric acid (200 mL). The organic phase was separated using a hydrophobic frit and was evaporated under reduced pressure to ca. 50 mL. The crude product was applied to 4×90 g silica Biotage™ columns on a Quad 3 system; each column being eluted with (i) 2:1 v/v ethyl acetate:cyclohexane (12×50 mL fractions), (ii) ethyl acetate (12×50 mL fractions), (iii) 9:1 v/v ethyl acetate:methanol to give (2R)-2-(2,4-difluorophenyl)-2-[(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-isobutyl-2,5-dioxopiperazin-1-yl]-N,N-dimethylethanamide (5.753 g, 62%) as a colourless solid.

Herkunft & Nachweise