An Improved Method for The Preparation Of The Phosphoramidites Of Modified 2′-Deoxynucleotides: Incorporation Of 8-Oxo-2′-Deoxy-7H-Guanosine Into Synthetic Oligomers

3′ -O-(Diisopropylamino-2-cyanoethoxyphosphinyl)-5′ -0-(4, 4′ -dimethoxytrityl)-N2-isobutyryl-8-oxo-2′-deoxy-7H-guanosine was synthesized and used for the introduction of an 8−0×0−2′-deoxy-7H-guanosine residue into a DNA oligomer by means of automated synthesis. A modification of the preparation of the phosphoramidite markedly improves the coupling efficiency in the oligomer synthesis in this and several other cases that were tested.