Preparation and cleavage reactions of 3′-thiouridylyl-(3′→5′)-uridine

Abstract

3′-Thiouridylyl-(3′→5′)-uridine [(Us)pU] 3 is prepared by coupling together the disulfide 14 and the 5′-H-phosphonate 18, and then removing the protecting groups. (Us)pU 3 readily undergoes cleavage in 0.05 mol dm⁻³ sodium glycinate buffer (pH 10.06) at 50 °C to give, in the first instance, uridine 4 and 3′-thiouridine 2′,3′-cyclic phosphorothioate 21; in glacial acetic acid at 30 °C, it rapidly undergoes cleavage in essentially the same way. The behaviour of (Us)pU 3 is compared with that of uridylyl-(3′→5′)-uridine (UpU) 1a under the same basic and acidic reaction conditions. (Us)pU 3 and 3′-thiouridine 2′,3′-cyclic phosphorothioate 21 are both substrates for ribonuclease A; (Us)pU 3 is a substrate for Crotalus adamanteus snake venom phosphodiesterase but not for calf spleen phosphodiesterase.