Phosphotriester approach deprotection

Phosphate triesters (18) are iatermediates ia both the phosphotriester and phosphoramidite methods, and under appropriate conditions for deprotection of the bases and cleavage of the support, can be obtained directiy by usiag these approaches. The ethyl and isopropyl esters have been obtained directiy by usiag the phosphoramidite method because these are stable duting the normal deprotection procedure (62). By changing the oxidizing agent to Sg, both amidate and triester thiolates can be obtained. 

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