3'- O-β-Glucosyl-4',5'-didehydro-5'-deoxyadenosine Is a Natural Product of the Nucleocidin Producers Streptomyces virens and Streptomyces calvus

3'-O-β-Glucosyl-4',5'-didehydro-5'-deoxyadenosine 13 is identified as a natural product of Streptomyces calvus and Streptomyces virens. It is also generated in vitro by direct β-glucosylation of 4',5'-didehydro-5'-deoxyadenosine 12 with the enzyme NucGT. The intact incorporation of oxygen-18 and deuterium isotopes from (±)[1-¹⁸O,1-²H₂]-glycerol 14 into C-5' of nucleocidin 1 and its related metabolites precludes 3'-O-β-glucosyl-4',5'-didehydro-5'-deoxyadenosine 13 as a biosynthetic precursor to nucleocidin 1.