Nucleic Acids Research, 1978, Vol. 5, No. 3 1029-1040
© 1978
Articles |
5'-Halogeno-2',3'-cyclic sulphite isomers in the preparation of 5'-halogeno nucleosides. Synthesis of 5'-deoxyuridine and 5'-deoxy-5-fluorouridine
ebabeck
i BeránekbInstitute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences 166 10 Prague 6, Czechoslovakia
b To whom correspondence should be addressed
Received February 3, 1978. When uridine (Ia) is reacted with thionyl chloride in hexamethylphosphoric triamide a mixture of isomeric 5'-chloro-2',3'-sulphites is formed, which can be separated to individual epimers IIa and IIIa, in 45% and 15% yields, respectively. Analogously, crystalline epimers IIb (37%) and IIIb (17%) can be obtained from 5-fluorouridine (Ib). Both isomers IIa, IIIa (or IIb, IIIb) afford a single 5'-chloro derivative IVa (or IVb, respectively) if treated with 0.1N sodium methoxide. From the mixture of sulphites IIa and IIIa (or IIb and IIIb) crystalline 5'-chlorouridine IVa is formed in 84.5% yield calculated per starting uridine Ia (or ctystalline 5'-chloro-5-fluorouridine IVb, 85.5% per starting 5-fluorouridine Ib. respectively). On reduction of 5'-chlorouridine IVa with tributyltin hydride 5'-deoxyuridine (Va) is formed in 79% yield. During the reduction of 5'-chloro-5-fluoro derivative IVb to 5-deoxy-5-fluorouridine (Vb, 57%) a partial reductive ,elimination of 5-fluorine takes place under formation of 5'-deoxyuridine (Va. 9%).