Syntheses and configurational analyses of thymidine 4-nitrophenyl [17O,18O]phosphates and the stereochemical course of a reaction catalyzed by bovine pancreatic deoxyribonuclease I

The syntheses of both diastereomers of thymidine 3'-(4-nitrophenyl [17O,18O]phosphate) [( 17O,18O]TpNP) and of thymidine 5'-(4-nitrophenyl [17O,18O]phosphate) [( 17O,18O]NPpT) and the Rp diastereomer of thymidine 3'-(4-nitrophenyl [17O,18O]phosphate) 5'-(4-nitrophenyl phosphate) [( 17O,18O]NPpTpNP) are described. The absolute configurations of the chiral phosphorus atoms have been determined unambiguously by 31P and 17O NMR spectroscopy. The Rp diastereomer of [17O,18O]NPpTpNP was hydrolyzed in the presence of bovine pancreatic deoxyribonuclease I to yield the Rp diastereomer of thymidine 3'-[16O,17O,18O]-phosphate 5'-(4-nitrophenyl phosphate), demonstrating that the enzyme-catalyzed reaction occurs by a mechanism in which a single displacement reaction occurs at the chiral phosphorus atom.