4 '-DTMP is a DHFR inhibitor with Ki of 5.1 nM (DHFR WT ) and 34.3 nM (DHFR L28R ), respectively. 4 '-DTMP carries a polar modification that induces additional local interactions with the enzyme . In particular, the hairpin structure on the M20 ring is related to the internal communication of the DHFR. 4 '-DTMP has potential inhibition of E.coli.