Diethyl Ether → N,N'-Dicyclohexylurea

Participants

Reaction Steps

30 g. of ribostamycin (the free base form) was added to 127 ml. of trifluoroacetic acid under ice-cooling and stirring, and the mixture was allowed to stand at ambient temperature overnight. The resulting solution of amber color was admixed with 400 ml of ethyl ether, and the admixture was cooled to precipitate 69 g of a salt of ribostamycin with trifluoroacetic acid which was then removed by filtration. A 20 g. portion of this ribostamycin trifluoroacetate was taken and then dissolved in 250 ml of tetrahydrofuran together with 16.4 g. of (S)-α-hydroxy-γ-N-phthalimido-n-butyric acid of the formula ##STR25## The solution was cooled with ice. A solution of 36.4 g of dicylcohexylcarbodiimide in 146 ml of tetrahydrofuran was prepared and cooled with ice. Both the solutions was combined together under ice-cooling and stirring. The combined solutions were agitated at ambient temperature for 2-3 hours and admixed with 8 ml of glacial acetic acid to decompose the excess of dicyclohexylcarbodiimide. 3286 mg of dicyclohexylurea produced was deposited and filtered off. The filtrate was concentrated to dryness, giving 43 g of a pale yellow colored solid comprising mixed trifluoroacetic acid salts of O-((S)-α-hydroxy-γ-N-phthalimido-n-butyryl)-ribostamycins.

Provenance & Evidence