Acetic Acid → N,N'-Dicyclohexylurea

Participants

Reaction Steps

2 g of the ribostamycin trifluoroacetate prepared in the same manner as in Example 1 was taken and dissolved in 35 ml of a liquid mixture of tetrahydrofuran and dimethylformamide (10:1 by volume). This solution was admixed with a solution of 1.74 g of (S)-α-hydroxy-δ-N-phthalimido-n-valeric acid in 16 ml of tetrahydrofuran. A solution of 3.62 g of dicyclohexylcarbodiimide in 16 ml of tetrahydrofuran was added thereto under ice-cooling. The mixture was agitated for 30 minutes under ice-cooling and agitated at ambient temperature for 1 hour 25 minutes to effect the esterification of the hydroxyl groups of the ribostamycin with the substituted valeric acid. The reaction mixture was admixed with 0.8 ml of glacial acetic acid and allowed to stand at ambient temperature overnight to decompose the excess of dicyclohexylcarbodiimide. The dicylcohexylurea by-produced which precipitated was removed by filtration. The filtrate was concentrated to give a solid comprising mixed trifluoroacetic acid salts of O-((S)-α-hydroxy-δ-N-phthalimido-n-valeryl)-ribostamycins.

Provenance & Evidence