Tandem oligonucleotide synthesis using linker (First Base) phosphoramidites.

First Base linker phosphoramidites add the first nucleoside to underivatized solid-phase supports using a regular phosphoramidite coupling cycle. A cleavable 3'-O-ester linkage allows NH4OH treatment to rapidly generate products with only 3'-OH ends. Either single or multiple sequences linked in tandem can be prepared and no additional deprotection steps are required.