(+/-)-[1-(2,4-Dichloro-pyrimidin-5-yl)-ethyl]-(4-methoxy-phenyl)-amine → 1-[2-(tert-butyl-diphenyl-silanyloxy)-1-(S)-methyl-ethyl]-7-chloro-3-(4-methoxy-phenyl)-4-methyl-3,4-dihydro-1H-pyrimido[4,5-d]pyrimidin-2-one

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Reaction Steps

(S)-tert-Butyl-2-isocyanato-propoxy-diphenylsilane (generated in situ from 0.440 g, 1.20 mmol, of (S)-(+)-3-(tert-butyl-diphenyl-silanyloxy)-2-methylpropionic acid) (from Example 13b supra) in hot toluene (2 mL; 120° C.) was treated with a solution of (±)-[1-(2,4-dichloro-pyrimidin-5-yl)-ethyl]-(4-methoxy-phenyl)-amine (0.35 g; 1.10 mmol) (from Example 1d supra) in toluene (2 mL). The resulting solution was kept at 120° C. for 30 minutes, then cooled to room temperature and concentrated. The residue was dissolved in anhydrous tetrahydrofuran (4 mL) and cooled in an ice-brine bath. Potassium tert-butoxide (1.0 M in tetrahydrofuran; 1.2 mL; 1.20 mmol) (Aldrich) was added dropwise and stirring continued in the cold for 15 minutes. The mixture was filtered through a bed of silica gel and eluted with ethyl acetate. Further purification with flash chromatography (Biotage 40 M; 25:75 ethyl acetate-hexanes) gave 1-[2-(tert-butyl-diphenyl-silanyloxy)-1-(S)-methyl-ethyl]-7-chloro-3-(4-methoxy-phenyl)-4-methyl-3,4-dihydro-1H-pyrimido[4,5-d]pyrimidin-2-one as a mixture of diastereomers. (Yield 0.31 g; 46%). No separation of diastereomers was seen at this time.

Provenance & Evidence