(η5-C5H5)Fe(CO)2-complexes of uridine and thymidine

The photochemical reaction of (η5-C5H5)Fe(CO)2I (FpI) with 2′,3′,5′-tri-O-acetyluridine (1a), 3′,5′-di-O-acetylthymidine (1b) and 5′-O-(4,4′-dimethoxytrityl)thymidine (1c) in benzene containing excess of diisopropylamine afforded corresponding Fp-complexes of N(3)-deprotonated nucleosides, 2a–c in moderate (45–75%) yields. Attempted removal of acetyl groups from 2a–b (K2CO3, MeOH–H2O, rt, 1 h or 25% NH3 aq., MeOH, rt, 2 h) gave unseparable mixtures of 3-Fp-uridine or 3-Fp-thymidine (3a–b) with uridine or thymidine. On the other hand, removal of the 4,4′-dimethoxytrityl groups from 2c proceeded smoothly in 80% acetic acid affording 3-Fp-thymidine (3b) in quantitative yield.