108 



H. GOBIND KHORANA 

 Example 2 



Structure 



Diagrammatic representation Abbreviation 



HOCH 2 /°\ Cytosine 



K, |>l 



O H 



/ 

 HO— P=0 



OCH 2 /°\ Adenine 



CAT 



O H 



/ 

 HO— P=0 



(^CH,/ 



d-CpApTp 



Thymine 



O H 



I 

 HO— P=0 



I 

 OH 



Full names: Deoxycytidylyl-(3' — > 5')-deoxyadenylyl-(3' — * 5')-thymidylic-(3') acid 



or 

 Deoxycytidylyl-(3' — > 5')-deoxyadenylyl-(3' — > 5')-thymidine-3' phos- 

 phate 



or 

 3'-0-Phosphoryl-thymidylyl-(5' -> 3')-deoxyadenyl.yl-(5' -* 3')-deoxy- 

 cytidine 



II. Chemical Synthesis of Polynucleotides 



It is now known with certainty that both the ribo- and deoxyribonucleic 

 acids consist of polynucleotide chains in which the individual nucleosides 

 are joined together by C 3 '-C 5 < phosphodiester bonds (Volume I, Chapter 

 12). As a logical development in the chemistry of these macromolecular sub- 

 stances, the chemical synthesis of polynucleotides has been undertaken 

 during the last few years. There the major problems are (1) the develop- 

 ment of phosphorylation methods for the formation of phosphodiester bonds 

 and (2) the preparation of suitably protected nucleosides or nucleotides so 

 as to leave only the desired (3'- or 5'-hydroxyl) function free for a phos- 

 phorylation reaction. Because of the complexity of these classes of com- 

 pounds it is inevitable that much effort will be expended on the problems 

 of the protecting groups. 



