INVERSE PHOSPHOTRIESTER DNA-SYNTHESIS USING PHOTOCHEMICALLY-REMOVABLEDIMETHOXYBENZOIN PHOSPHATE PROTECTING GROUPS

A method has been developed to prepare short DNA sequences using light to deprotect a nucleoside 3'-phosphotriester, generating a phosphodie ster useful for coupling with a free 5'-OH-nucleotide. The dimethoxybe nzoin group is used as the photochemically-removable protecting group for the 3'-phosphate. Cyanoethyl is most effective as the second prote cting group on the phosphodiester. Because the method is directed at t he preparation and use of the DNA sequences while still bound to the s upport, allyl and allyloxycarbonyl protecting groups are used for the nitrogenous bases since, based on the work of Hayakawa and Noyori, the y can be removed without cleaving the DNA from the support. Two simple trinucleotides have been prepared in solution using this method. It h as been demonstrated that the photochemical deprotection conditions do not lead to the formation of cyclobutane dimers from adjacent T resid ues.