Résumé
This unit provides a modified phosphoramidite method to synthesize oligodeoxyribonucleotides onto a universal and reusable hydroxyl solid support thanks to the use of deoxyribonucleoside tert-butyl and cyanoethyl phosphoramidites. The nucleoside tert-butyl phosphoramidite allows the introduction of an H-phosphonate diester linkage using the phosphoramidite method. After elongation, the H-phosphonate diester linker is cleaved by transesterification under mild basic conditions to yield an oligonucleotide with free 3'- and 5'-hydroxyls and the starting solid support. Thus, the solid support is easily recycled and used for a subsequent synthesis. In addition, a nucleoside tert-butyl phosphoramidite could be introduced inside the oligonucleotide chain during the elongation to yield a second H-phosphonate diester linkage. After elongation, the two H-phosphonate diester linkages are cleaved, producing two oligonucleotides with free 3'- and 5'-hydroxyls.