5 -Phosphoryl oligonucleotides synthesis

On use of N,N -dicyclohexylcarbodiimide instead of sulfonyl chlorides as condensation reagent in oligonucleotide synthesis, then the pyro-, tri- and tetraphosphate stages are again involved 124). The metaphosphate 183 a is found in small amounts by 3iP-NMR spectroscopy, but again no cyclic trimetaphosphate 184 can be detected, which would also be a possible phosphorylation reagent. 

Phosphorylation, This reagent is useful for the first step in the phosphotriester approach to oligonucleotide synthesis,which involves conversion of a free 3 -hydroxy group of a protected nucleoside into a phosphotriester of type 3. Treatment of 3 with p-thiocresol and triethylamine at 20° leads to the triethyl-... 

Enol pyrophosphates Figure 6. Some new phosphorylation/condensation reagents for oligonucleotide synthesis. 

The most widespread use of 1,2,4-triazole continues to be as a catalyst for the transfer of acyl groups, phosphoryl groups, and phosphite groups. Its greatest utility has been in the various methods of oligonucleotide synthesis, e.g., the phospho-ramidite method, //-phosphonate method, and phosphotriester approach. Its use has been extended to the synthesis of phos-phorothioates (eq 6). ... 

Chattopadhyaya, J. B. and Reese, C. B. (1979) Some observations relating to phosphorylation methods in oligonucleotide synthesis. Tetrahedron Lett, 20, 5059-5062. 

Extension of general oligonucleotide synthesis using phosphotriester protection to allow insertion of terminal 5 -phosphates Selective removal of 5 -triphenylmethoxyacetyl groups allows phosphorylation by TPS-activated mono-2, 2, 2-tri chi oroethyl phosphate on protected oligomers. ... 

Given the good yields and simplicity of the process, this procedure has been used to prepare intermediates for oligonucleotide synthesis, e.g. in the synthesis of 5 -0-monomethoxytritylthymidine 3 -phenylphosphate (7) (eq 3). Phosphorylation of 5 -0-monomethoxytritylthymidine (5) gave the protected nucleoside phosphate (6) in 98% yield which, after removal of the aniline protecting group and workup, gave the pyridinium salt in 85% yield. 

As mentioned in last year s Report, aromatic phosphoramidates have been used to protect 5 -phosphoryl groups in the stepwise synthesis of oligodeoxyribonucleotides. The appropriate monomer units are coupled with DCC and the phosphoramidate protecting group is removed when required with isoamyl nitrite. A rapid and general preparative method for oligonucleotides has been developed based on phosphoramidates of the highly lipophilic 4-aminophenyltriphenylmethane (25). Purification of... 

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