31698-14-3

Cyclo-C,Kohjin,Japan,1975

Ancitabine is an antineoplastic. Also, it is an agent demonstrating strong synergistic interaction with irofulven, which possesses antitumor activity against solid tumors.

ChEBI: An organic heterotricyclic compound resulting from the formal condensation of the oxo group of cytidine to the 2' position with loss of water to give the corresponding cyclic ether. A prodrug, it is metabolised to the antineoplastic agent cytarabine, so is used to maintain a more constant antineoplastic action.

A series of reaction steps may be employed in which: (1) Uridine is reacted with trityl chloride to give 5'-o-trityluridine; (2) Imidazole is reacted with thiophosgene and that product reacted with the 5'-o-trityluridine to give 2,2'- anhydro-1-(5'-o-trityl-β-D-arabinofuranosyl)uracil; (3) The preceding uracil product is converted to the thiouracil using hydrogen sulfide; (4) The trityl group is removed by treatment with 80% acetic acid; (5) A triacetylated product is obtained using acetic anhydride; (6) A dithiouracil is prepared from the uracil intermediate using phosphate pentasulfide.
Preparation of 1-(β-D-arabinofuranosyl)-2-thiocytosine: A solution of 2.0 g of 1-(2',3',5'-O-triacetyl-β-D-arabinofuranosyl)-2,4-dithiouracilin 100 ml of methanol is saturated with anhydrous ammonia at 0°C. The mixture, in a glass liner, is heated in a pressure bomb at 100°C for three hours. The reaction mixture is concentrated to a gum in vacuum, and most of the byproduct acetamide is removed by sublimation at 60°C/0.1 mm. The residue is chromatographed on 100 g of silica gel. Elution of the column with methylene chloride-methanol mixtures with methanol concentrations of 2-25% gives fractions containing acetamide and a series of brown gums. The desired product is eluted with 30% methanol-methylene chloride to give a total yield of 0.386 g (30%), MP 175-180°C (dec.). Recrystallization from methanolisopropanol furnishes an analytical sample, MP 180-182°C (dec.).
To a solution of 80 mg of 1-(β-D-arabinofuranosyl)-2-thiocytosine in 12 ml of water is added dropwise 3 ml of a 1 M bromine solution in carbon tetrachloride. At this point the color of the bromine persists for about 2-3 minutes after each addition. The unreacted bromine is blown off with a stream of nitrogen, and the reaction mixture is concentrated to a syrup in vacuum using a bath temperature less than 50°C. The residue is evaporated three times with 10 ml portions of ethanol, whereupon it crystallizes. The product is triturated with cold ethanol and with ether to obtain 17 mg of 2,2'-anhydro-1- (β-D-arabinofuranosyl)cytosine hydrobromide, MP 240°C (dec.).
Treatment of the hydrobromide with a slight excess of ethanolic ammonia yields the base which may then be converted to the hydrochloride.

Antineoplastic