Henry W. Dion

ISOLATION AND PROPERTIES OF A VIDARABINE DEAMINASE INHIBITOR, CO-VIDARABINE

A potent vidarabine (9-@-~-arabinofuranosyladenine) and adenosine deaminase inhibitor, co-vidarabine (la, FIGURE I ) , has been isolated in crystalline form from the culture filtrates of a strain of Srreproniyces antibioricus N R R L 3238. The structure of the inhibitor has been elucidated and defined chemically as (R)-3-(2-deoxy-P-~ervihro-pentofuranosyl)-3,6,7,8-tetra hydroimidazo[4,5-d][ I ,3]diazepin-8-01. Preliminary chemical studies on culture filtrates demonstrated that the inhibitor was very sensitive to pH. Stability studies at room temperature indicated the necessity of doing the fractionation work within the pH range of 7-9.5 since the desired compound is very labile in the acid range. Because the inhibitor exhibits little or no antibacterial or antifungal activity. all of the fracticnation work was monitored by means of enzyme activity initially and then later on by uv. Extraction of culture filtrates with typical organic solvents was unsuccessful. Ion exchange using the usual cation or anion resins was fruitless because the resins either failed to adsorb the inhibitor or destroyed the compound during the process. The isolation scheme that proved successful consisted of the following steps: ( I ) concentration of the filtered beer in vacuo at 3035°C at pH 9.2 to I/lOth of the original volume; (2) chilling of the concentrate to remove insoluble products; (3) rediluting of the filtered concentrate with water to the original beer volume; (4) batch carbon adsorption and elution therefrom with 25?,, aqueous acetone; (5) concentration of the carbon eluate and precipitation of insolubles from 80,,, methanol solu-