Nucleotides phosphoramidite coupling

A last possibility to obtain probes grafted onto beads is to directly synthesize the oligonucleotide probes onto glass beads via phosphoramidite reaction [18] (Fig. 6). The synthesis reaction sequence is composed of a coupling step between a protected nucleotide immobilized onto the bead and a tetra-zole activated and protected nucleotide (step C). This is followed by a capping and a de-blocking of the newly added nucleotide (step D and B). The cycle is then repeated until the desired sequence is obtained. 

This group was developed for 5 -hydroxyl protection in oligonucleotide synthesis. It is stable to the conditions for nucleotide coupling using the phosphoramidite approach. It is not stable to acid or to 12/pyridine/THF, conditions used for phosphite oxidation. It has been used to prepare a 20-mer. ... 

Nucleotide coupling (addition of next protected nucleoside phosphoramidite)... 

Figure 8.7 Schematic representation of split-and-pool combinatorial nucleotide synthesis. An example of split-and-pool (split-and-combine) synthesis of trideoxyribonucleotides complementary to codons by the sohd phase phosphoramidite nucleotide synthesis is illustrated. Each cycle in the synthesis includes spht (equal molar spUt), react (deprotection, coupling with 4 protected nucleotides and oxidation) and combine steps. After 3 cycles of 4 reactions (corresponding to couphng reactions with 4 nucleotides per cycle), the final combined library consists of a mixture all 64 trinucleotides...

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