Collect. Czech. Chem. Commun. 1996, 61, 627-644

Preparation of 5-Benzyluracil and 5-Benzylcytosine Nucleosides as Potential Inhibitors of Uridine Phosphorylase

Marcela Krečmerová, Hubert Hřebabecký and Antonín Holý

Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague 6, Czech Republic


Reaction of 3,4,6-tri-O-acetyl-2-deoxyglucopyranosyl bromide (1) with silylated 5-benzyluracil and subsequent ammonolysis afforded α- and β-anomers of 5-benzyl-1-(2-deoxy-D-glucopyranosyl)uracil (2 and 3). Under catalysis with tin tetrachloride, silylated 5-benzyluracil reacted with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose to give 2',3',5'-tri-O-benzoyl-5-benzyluridine (10), which was converted into the 4-thio derivative 11 by reaction with Lawesson reagent. Debenzoylation of compound 11 afforded 5-benzyl-4-thiouridine (12), whereas its reaction with methyl iodide and deblocking gave 4-methylthiopyrimidine nucleoside 14. Amonolysis of derivative 12 at elevated temperature afforded 5-benzylcytidine (15). This reacted with thionyl chloride at room temperature to give cyclic sulfite 16 which on heating at 100 °C in dimethylformamide was converted into 5-benzyl-2,2'-cyclocytidine (17). Mild alkaline hydrolysis of compound 17 afforded 1-(β-D-arabinofuranosyl)-5-benzylcytosine (18). With boiling thionyl chloride, compound 15 formed 2',3'-cyclic sulfite 19 which on alkaline hydrolysis gave 5-benzyl-5'-chloro-5'-deoxycytidine (20). Compound 20 was reduced with tributylstannane to 5-benzyl-5'-deoxycytidine (21). Reaction of silylated 5-benzyluracil with 2-deoxy-3,5-bis(O-p-toluoyl)-D-ribofuranosyl chloride, catalyzed with mercury(II) bromide, afforded 5-benzyl-2'-deoxy-3',5'-bis(O-p-toluoyl)uridine (22) and its α-anomer 23. With Lawesson reagent, compound 22 gave 5-benzyl-4-thiouracil derivative 24 which was ammonolyzed to give 5-benzyl-2'-deoxycytidine (25). Analogously, compound 23 was converted into 5-benzyl-2-deoxy-α-cytidine (27). 5'-O-Benzoyl-5-benzyluridine (29) was converted into the 2,2'-anhydro derivative 30 which on reaction with hydrogen chloride afforded 3'-chloro-3'-deoxynucleoside 31. This compound was reduced with tributylstannane and the obtained 2'-deoxynucleoside 32 on treatment with thionyl chloride gave a mixture of erythro- and threo-3'-chloro-2',3'-dideoxynucleosides (33 and 34, respectively) which were reduced to 5'-O-benzoyl-5-benzyl-2',3'-dideoxyuridine (35). Compound 35 reacted with Lawesson reagent under formation of 4-thiouracil derivative 36 and this was deblocked to 5-benzyl-4-thio-2',3'-dideoxyuridine (37). On heating with ammonia, compound 37 was converted into 5-benzyl-2',3'-dideoxycytidine (38). Reaction of 4-thiouracil derivative with methyl iodide and subsequent hydrazinolysis afforded 4-hydrazino derivative 40 which was heated with silver oxide in ethanol to give a mixture of anomeric 5-benzyl-1-(2,3-dideoxyribofuranosyl)-2(1H)-pyrimidinones (42).

Keywords: 5-Benzyluracil; Pyrimidine; Nucleosides; Uridine phosphorylase.