In 1978 a synthesis of 5'-(R)-[2H1]-adenosine was devised by the principal investigator. This synthesis makes possible the investigation of the stereochemistry of enzymatic reactions that involve C-5' of the adenosine nucleus. Three enzymes are proposed for stereochemical study: methionine S-adenosyltransferase, S-adenosylhomocysteinase, and B12S-adenosyltransferase. Each of these enzymes plays an important role in living systems and stereochemical information will provide important insight into the mechanisms of the reactions they catalyze. In addition, the chirally deuterated adenosine has been converted into 5'-(R)-[2H1]-coenzyme B12. The deuterated coenzyme is being used to investigate the mechanism of carbon-cobalt bond cleavage associated with the reaction catalyzed by the enzyme propanediol dehydrase.