5-[(Hydroxymethyl)-O-pyrophosphoryl]uracil, an intermediate in the biosynthesis of .alpha.-putrescinylthymine in deoxyribonucleic acid of bacteriophage .vphi.W-14

In a nonpermissive host, an amber mutant, am 37, of bacteriophage phi W-14 synthesizes deoxyribonucleic acid (DNA) of considerably greater buoyant density than the DNA synthesized by wild-type phage. The am 37 DNA lacks the hypermodified pyrimidine, alpha-putrescinylthymine (putThy). Instead, it contains a new modified base, 5-[(hydroxymethyl)-O-pyrophosphoryl]uracil (hmPPUra). Extracts of cells infected with wild-type phi W-14 convert the hmPPUra in am 37 DNA to putThy when incubated with putrescine.