Efficient and flexible access to fully protected trinucleotides suitable for DNA synthesis by automated phosphoramidite chemistry

An efficient synthetic approach to protected trinuclotide phosphoramidites suitable for codon-by-codon synthesis of structural gene combinatorial libraries is described; the procedure rests on the use of pair of orthogonal protecting groups for the two oligomer termini and offers flexibility in the choice of chain elongation direction going from dimer to trimer.