Hydration at C5'-C6' double bond of adenosine substrates by S-adenosyl-L-homocysteine hydrolase.

It was previously demonstrated that (E)-5',6'-didehydro-6'-deoxy-6'-fluorohomoadenosine (EDDFHA) undergoes addition of water across the isolated C5'-C6' double bond by S-adenosyl-L-homocysteine (AdoHcy) hydrolase without prior oxidation at C3' (J. Biol. Chem.1993, 268, 17030). Addition of water at the 5' position results in the formation of 6'-deoxy-6'-fluoro-5'-hydroxyhomoadenosine (DFHHA). We now describe preparation of EDDFHA, its Z-isomer and their 6'-[2H]-labeled analogues as well independent syntheses of DFHHA and 6'-deuterio-DFHHA. These compounds allow the assignment of absolute configuration at the 5' carbon atom of DFHHA as well as a determination of the overall stereochemistry of enzymatic addition of water at the 5' carbon atom and protonation at the 6' carbon atom.