Hydrochloric Acid → Cytarabine

A solution of the diacetyl derivative (30 mg.) of the carbocyclic analog of cyclocytidine, described immediately above, in methanol (15 ml.) saturated with hydrogen chloride was stirred at room temperature overnight. Evaporation of volatile components with a stream of nitrogen, then under reduced pressure, and in a high vacuum left the hydrochloride of the carbocyclic analog of cyclocytidine (30 mg.); the mass spectrum included the expected peaks (m/e 223, 206, 192). A solution of this material in 1 N aqueous ammonia (2 ml.) was heated at 80°-85° for 5 min. Volatile components were evaporated under reduced pressure and, then, in a high vacuum. Crystallization of the residue from ethanol gave the carbocyclic analog of 1-β-arabinofuranosylcytosine. This compound may also be isolated by ion-exchange chromatography, by preparative thin-layer chromatograhy, or by the sequential use of these techniques after impure preparations containing the carbocyclic analog of cyclocytidine are treated with aqueous ammonia. The properties of the pure compound prepared by the procedure of either Part A or Part B are summarized in Part A.