Automated chloridite and amidite synthesis of oligodeoxyribonucleotides on a long chain support using amidine protected purine nucleosides

Preparation of solid supports with long aliphatic spacer for the oligonucleotide synthesis is described. Automated synthesis of oligodeoxyribonucleotides using in situ prepared methylchlorophosphite intermediates from amidine protected purine nucleosides is described. Phosphoramidite synthesis of oligodeoxyribonucleotides mediated by 1-methylimidazole trifluoromethanesulfonate is described. Novel isolation of crude oligonucleotides by ethanol precipitation of potassium salts is described.