4-(1,2,4-Triazol-1-yl)- and 4-(3-nitro-1,2,4-triazol-1-yl)-1-(β-<scp>D</scp>-2,3,5-tri-O-acetylarabinofuranosyl)pyrimidin-2(1H)-ones. Valuable intermediates in the synthesis of derivatives of 1-(β-<scp>D</scp>-arabinofuranosyl)cytosine (ara-C)

Abstract

Treatment of the acetylated derivative (3b), which was prepared from uridine in 86% overall yield, with tri(1H-1,2,4-triazol-1-yl)phosphine oxide gave compound (6a) in high yield, and with 3-nitro-1,2,4-triazole and diphenyl phosphorochloridate it gave compound (6b) in high yield. When the former product (6a) was allowed to react with ammonia, methylamine, dimethylamine, and morpholine at room temperature, and the products further deacetylated if necessary, ara-C (1; R1= R2= H) and its corresponding 4-N-alkyl derivatives (1; R1= H, R2= Me), (1; R1= R2= Me), and [1; R1,R2=–(CH2)2O(CH2)2–] were obtained in very high yields. 4-N-Phenyl-ara-C (1; R1= H, R2= Ph) was obtained in high yield when compound (6a) or (6b) was heated with aniline in pyridine solution and the products then deacetylated. The nitro-compound (6b) was converted into the ara-C derivative (1; R1= H, R2= CH2CO2Me), and the sulphide (7) was obtained following the deacetylation of the products of the reaction between the 1,2,4-triazolyl derivative (6a), toluene-p-thiol, and triethylamine.