2,4-Diamino-5-benzylpyrimidines and analogs as antibacterial agents. 2. C-Alkylation of pyrimidines with Mannich bases and application to the synthesis of trimethoprim and analogs

Abstract
A new route to 5-(p-hydroxybenzyl)pyrimidines was developed which utilizes phenolic Mannich bases plus pyrimidines containing at least 2 activating groups. The products can be alkylated on the phenolic 0 or on the pyrimidine N-1 atom, depending on conditions. This method was used to prepare trimethoprim, a broad-spectrum antibacterial agent, starting from 2,4-diaminopyrimidine and 2,6-dimethoxyphenol.