Chemical synthesis of the 24 RNA fragments corresponding to hop stunt viroid.

A general and practical synthetic method of oligoribonucleotides (10-20 mers) by using the cyanoethyl phosphoramidite approach was described. In this experiment 9-phenylxanthen-9-yl (Pix) and 9-(4-methoxy)phenylxanthen-9-yl (Mox) groups were employed for the 5'-hydroxyls and tetrahydropyranyl (Thp) group was used for the 2'-hydroxyl protecting groups. In addition, suitable acyl groups were introduced for the protection of the lactam functions of guanine and uracil moieties.