Nucleoside 5′-C-phosphonates: reactivity of the α-hydroxyphosphonate moiety
摘要:
We found that various dialkyl phosphites, dialkyl trimethylsilyl phosphites, and tris-trimethylsilyl phosphite reacted smoothly with nucleoside 5'-aldehydes to afford epimeric nucleoside 5'-C-phosphonates in high yields. A number of these compounds in both the 2'-deoxyribo and ribo series were prepared. In the case of 2'-deoxythymidine-5'-aldehyde, a thorough study was made on the influence of the 5'-hydroxyl protecting group, type of phosphite, base, and solvent, on the yield and epimeric ratio of the resulting 5'-hydroxyphosphonates. Partial stereoselectivity in favour of either R or S epimers was observed. An attempt to transform the alpha-hydroxyl of the phosphonate moiety into a halo or azido moiety was not Successful. Only intramolecular substitution reaction of the mesyloxy group for an alkoxy residue of the 2-hydroxyethyl ester took place in a low yield. (c) 2006 Elsevier Ltd. All rights reserved.