Some observations relating to phosphorylation methods in oligonucleotide synthesis

A very convenient procedure for the conversion of ($\text{N}$),O-5′-protected deoxyribonucleosides ($\text{8}$) into the triethylammonium salts of the corresponding 3′-($\text{o}$-chlorophenyl) phosphates ($\text{9}$) is described. Good yields of partially-protected 3′→5′-dinucleoside phosphates ($\text{10}$) are obtained from the latter ($\text{9}$) and 3′-unprotected nucleoside building blocks ($\text{12a}$).