Synthesis and absolute stereochemistry of the two diastereoisomers of P 3 -1-(2-nitrophenyl)ethyl adenosine triphosphate (‘caged’ ATP)

1 -(2-Nitrophenyl)ethanol was resolved by fractional crystallisation of its diastereoisomeric (1S)-cam-phanates. The absolute stereochemistry of the (S)-alcohol was determined using the Horeau kinetic resolution procedure, and subsequently confirmed by X-ray crystallography of its (1S)-camphanate ester. The resolved alcohols were converted to (R)- and (S)-1-(2-nitrophenyl)ethyl phosphates, each of which was condensed with adenosine diphosphate to give the (R)- and (S)-1-(2-nitro-phenyl)ethyl P3-esters of adenosine triphosphate.