P. M. J. Burgers

Phosphorylation of nucleoside derivatives with aryl phosphoramidochloridates

Abstract The preparation of three aryl phosphorocyclohexylamidochloridates ( 7a , 7b and 7c ) and an aryl phosphoromorpholidochloridate ( 8 ) is described. These aryl phosphoramidochloridates react with 2′,3′-O-methoxymethylene-uridine, -4-N-anisoylcytidine and -6-N-anisoyladenosine ( 9a , 9b and 9c , respectively), in the presence of the 1-ethylimidazole derivative ( 11a ) to give high yields of the corresponding fully-protected 5′-phosphoramidates ( 10 ). Treatment of the latter compounds with aqueous alkali gives the nucleoside 5′-phosphoramidate derivatives ( 14 ) which, on mild acidic hydrolysis, give the corresponding unprotected 5′-nucleotides ( 15 ) in virtually quantitative yields. Phosphorylation of 2′-O-methoxytetrahydropyranyluridine ( 12 ) with 7a and 8 , under the same conditions, occurs regiospecifically to give the corresponding 5′-phosphoramidate derivatives ( 13 ). The partially-protected dinucleoside phosphate ( 16b ) has been prepared and phosphorylated with 7a to give, after removal of the protecting groups, the dinucleotide ( 18 , pUpU) in high yield.

3′,5′-Cyclic dinucleoside phosphates: undesirable intermediates in the phosphotriester approach to oligonucleotide synthesis

Mild alkaline hydrolysis of (4a) gives the 3′,5′-cyclic dinucleoside phosphate (5a); more drastic alkaline hydrolysis of phosphotriester intermediates with free vicinal 5′- or 3′-hydroxy functions [(4a) and (7b), or (6a) and (8b)] leads to products with, respectively, 5′→ 5′- or 3′→ 3′-in addition to 3′→ 5′-internucleotide linkages.

Preparation of nucleoside 3′,5′-cyclic phosphates via phosphotriester intermediates

Several ribonucleoside 3′,5′-cyclic phosphates (7b) have been prepared in good yields by the action of base on the corresponding 2′-protected 3′-diphenyl phosphates (5); thymidine 3′,5′-cyclic phosphate (7; R = H, B = thymine-1) has similarly been prepared from both thymidine 3′- and 5′-diphenyl phosphates (8a and 8b).

Approaches to oligoribonucleotide synthesis via phosphotriester intermediates

Methods are described for the synthesis of uridylyl-(3′→ 5′)-uridine and uridylyl-(3′→ 5′)-uridylyl-(3′→ 5′)-uridine, in good yields a phosphotriester approach has been adopted with the internucleotidic linkages protected by aryl protecting groups.