Synthesis of deoxyadenosine‐5′‐(35S)‐thiomonophosphate [dAMP(35S)] of high specific activity – a key intermediate for the synthesis of Sp‐deoxyadenosine‐5′‐(alpha;‐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 ³⁵S (specific activity>1000 Ci/mmol) in toluene solution to give deoxyadenosine‐5′‐(³⁵S)‐thiomonophosphate [dAMP(³⁵S)] 3 . Enzymatic conversion of deoxyadenosine‐5′‐(³⁵S)‐thiomonophosphate to Sp‐deoxyadenosine‐5′‐(α‐³⁵S)‐thiotriphosphate [Sp‐dATP (α‐³⁵S)] 5 was carried out following a standard reaction protocol. Copyright © 2001 John Wiley & Sons, Ltd.