Synthesis of deoxyadenosine-5′-(35S)-thiomonophosphate [dAMp(35S)] of high specific activity -: a key intermediate for the synthesis of Sp-deoxyadenosine-5′-(α-35S)thiotriphosphate [Sp-dATP (α-35S)]

Unprotected deoxyadenosine 1 was treated with an excess of phosphorus acid and stoichiometric proportions of N, N'-di-p-tolylcarbodiimide in anhydrous pyridine to give deoxyadenosine-5'-monophosphite 2. The latter was activated with trimethylsilyl chloride followed by sulphurisation with elemental S-35 (specific activity > 1000 Ci/mmol) in toluene solution to give deoxyadenosine-5'-(S-35)-thiomonophosphate [dAMp(S-35)] 3. Enzymatic conversion of deoxyadenosinc-5'-(S-35)-thiomonophosphate to Sp-deoxyadenosine-5'-(alpha-S-35)-thiotriphosphate [Sp-dATP (alpha-S-35)] 5 was carried out following a standard reaction protocol. Copyright (C) 2002 John Wiley Sons, Ltd.