Synthesis of Oligo and Polynucleotides

Techniques for both the chemical and enzymatic synthesis of nucleic acids have been extensively developed over recent decades. Of particular importance is the synthesis of short-chain oligonucleotides for purposes of genetic engineering (Chapter 11.6). 

The first laboratory synthesis of a di-nucleotide containing a 3 -5 linkage (10.81) was carried out by Michelson and Todd [30] as long ago as 1955. Since that time, and particularly during the last decade 

Most modern methods (for DNA or RNA) are essentially combinations of improved chemical and biochemical techniques of this kind. Polymers containing over 150 nucleotide units have been made, and their laboratory synthesis has now become a subject of great importance in connection with the preparation of artificial genes for use in genetic engineering. Genes can be effectively copied by PCR (Chapter 11.6). 

Alternatively, condensations of the type (10.82b) produced elongation in the 3 5 direction. 

Condensing agents which have been used include dicyclohexylcarbodiimide (10.83a) and triisopropylbenzene sulphonyl chloride (10.83b). The 5 OH position can be protected by monomethoxy-trityl (10.83c) and the base amino groups by such groups as anisoyl (10.83d) or isobutyryl (10.83e). 

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