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Abstract

Reaction of 5'-O-tritylribonucleosides I with dimethyl p-toluenesulfonyloxymethanephosphonate (III) followed by hydrolysis afforded 2'(3')-O-phosphonylmethyluridine (IIa), -cytidine (IIb) and -adenosine (IIc). With 2',5'-di-O-trityluridine (IX), this procedure led to the 3'-isomer of IIa, with 3',5'-di-O-trityluridine (X) to the 2'-isomer. 5'-O-Trityluridine (Ia) and -cytidine (Ib) were converted by reaction with iodomethanephosphonic acid and N,N'-dicyclohexylcarbodiimide into the 2'(3')-O-iodomethanephosphonyl derivatives IVa, b which on reaction with sodium hydride and subsequent hydrolysis gave the compounds IIa and IIb. Reaction of compound I or 5'-O-benzoyluridine (VIII) with chloromethanephosphonyl dichloride (V) and removal of the protecting groups afforded 2'(3')-O-chloromethanephosphonylribonucleosides VI which on reaction with sodium hydride, or better with aqueous alkali, gave 2'(3')-O-phosphonylmethyl derivatives of uridine (IIa), cytidine (IIb), adenosine (IIc) and guanosine (IId). 2',3'-O-Isopropylideneribonucleosides XI reacted with the compound V to give, after hydrolysis, 5'-O-chloromethanephosphonyluridine (XIIa) and cytidine (XIIb). These compounds were not affected by an alkali metal hydride or hydroxide.