Nucleic Acids Research: VOLUME 37 ISSUE 5 2009

The interaction of 3-0-acetyldithymidilate (pdTpdl(Ac)), thymidine-3',5'-diphosphate (pdTp; and thynd.dine-3'-phenylphosphate-5'-phosphate (pdTpPh) with 2,4,6-triisopropylbenzene sulphonyl chloride (TPS) and II.N-dicyclohexylcarbodiinri.de (DCC) in pyridine and dimethylformamide (DMP) was studied by pulsed NMR spectroscopy on phosphorus nuclei. Thymidine cyclic 3« ,5'-pyrophosphate and dimeric pyrophosphate derivatives were shown to be the main products of the reaction of pdTp with TPS and SCC. The former shows spin AB-syatem with the unusually large spin-spin coupling constant about 28Hz upfield to the signals of the dimeric pyrophosphates in NHR spectrum. Analof spin AB-systems with large spin-spin coupling constants up to 32 Hz) were observed in the spectra of the reaction mixtures of pdTpdT(Ac) with TPS or DCC and of pdTpPh with TPS. These spin AB-systems were ascribed to 3',5'-cyclic pyrophosphate derivatives of pdTpdT(Ac) and pdTpPh. IHTRODUCTIOir Recently it was found by pulsed P NMR spectroscopy that the interaction of mononucleotide with 2,4,6-triisopropylbenzenesulphonyl chloride (TPS) in pyridine results in the formation of highly reactive monomeric nucleotide derivative (compound B» nacleoside-5-metaphoaphate or its pyridinium derivative) . This derivative reacts readily with phosphodiester groups forming trisubstituted pyrophosphates (compounds of type C). Thus the reaction of S'-O-trltylthymidilyl-O'—r5' )-3»-0-acetylthymidine with the B type derivative of 3'-0-acetylthymidine-5-phosphate results in the immediate formation of P*-5'-0-tritylthymidine P« ,P>-bis-(3'-O-aoetylthymidine)pyrophosphate (C, R • 5'-0-tritylthymidine; R',R" = 3'-0-acetylthymidine) . *Part VIII: see Ref. © Information Retrieval Limited 1 Falconberg Court London W1V5FG England 1401 Nucleic Acids Research