Spectrum Chemical manufactures and distributes fine chemicals with quality you can count on including those with CAS number 6112-76-1, Whether you call it Mercaptopurine, 1 -7-Dihydro-6H-purine-6-thione Monohydrate , Purine-6-thiol or Purinethiol you can be assured the Mercaptopurine products offered by Spectrum, meet or exceed the grade requirements or specifications for each individual product.