Hydrochloric Acid → (8S,9R)-2,3,8-Trimethyl-8-hydroxy-9-phenyl-7,8,9,10-tetrahydroimidazo[1,2-h][1,7]naphthyridin-7-one

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Reaction Steps

20 g of (8R,9R)-2,3-dimethyl-8-hydroxy-9-phenyl-7,8,9,10-tetrahydroimidazo[1,2-h][1,7]naphthyridin-7-one (WO 98/42707) are dissolved in 100 ml of dichloromethane, and the solution is treated with 4 g of tetrabutylammonium hydrogensulfate, 70 ml of 50% strength aqueous sodium hydroxide solution and with 5 ml of methyl iodide, stirred vigorously at room temperature for 16 h, adjusted to pH 7 using ½ conc. hydrochloric acid with cooling and extracted three times with 100 ml of dichloromethane each time. The organic phases are combined, washed twice with a little water and concentrated to dryness on a rotary evaporator, and the residue obtained is purified twice on silica gel (1st eluent: dichloromethane/methanol 100/3; 2nd eluent: dichloromethane/methanol 100/1). 7.9 g of the title compound are obtained as a yellowish crystallizate of melting point 240° C.

Provenance & Evidence