. "\"The chemical reactions and pathways resulting in the formation of pyrimidine nucleobases, 1,3-diazine, organic nitrogenous bases, beginning with the synthesis of a pyrimidine ring from simpler precursors.\" [GOC:mah, ISBN:0716720094]" . . "'de novo' pyrimidine nucleobase biosynthetic process" . "'de novo' pyrimidine base biosynthesis" . "'de novo' pyrimidine base anabolism" . "'de novo' pyrimidine base biosynthetic process" . "'de novo' pyrimidine base formation" . "'de novo' pyrimidine base synthesis" . .