Thymine-d4 is a deuterated compound of Thymine. Thymine has a CAS number of 65-71-4. One of the pyrimidine bases of living matter. Derivation: Hydrolysis of deoxyribonucleic acid, from methylcyanoacetylurea by catalytic reduction. Use: Biochemical research. Thymine is a pyrimidine nucleobase. As the name implies, thymine may be derived by methylation of uracil at the 5th carbon. Thymine is found in the nucleic acid DNA. In RNA thymine is replaced with uracil in most cases. In DNA, thymine binds to adenine via two hydrogen bonds to assist in stabilizing the nucleic acid structures.