Design and Synthesis of Histidine Analogues of Folic Acid and Methotrexate as Potential Folylpolyglutamate Synthetase Inhibitors

Abstract

Folypolyglutamate synthetase (FPGS) is responsible for the conversion of naturally occurring folates and antifolates to their poly-gama-glutamyl derivatives, which are the forms required for intracellular retention of folates and are also the preferred substrates (cofactors) for most folate-dependent enzymes. Folate and methotrexate analogues 6 and 4, with L-histidine in place of L-glutamate, were designed and synthesized as potential FPGS inhibitors. Target compound 5, the N tau-(carboxymethyl)-L-histidine derivative of 4, was also prepared. Compounds 4 and 5 inhibited the growth of L1210 cells (IC50 values: 0.091 and 0.15 microM, respectively) and were potent inhibitors of L1210 dihydrofolate reductase. No significant inhibition of FPGS by 4, 5, or 6 was observed at the high pH of the standard enzyme assay. This could be the consequence of a lack of protonation of the basic side chains, which is likely to be required for FPGS inhibitory activity. The observed cytotoxicity indicates that partial protonation of the imidazole ring permits cellular uptake of the analogues.

Calorimetric Studies of Ligand Binding in R67 Dihydrofolate Reductase

“…The synthesis of 2-aza-2-deamino-N 10 -methyl-5,8-dideazafolic acid (ADMDF), N R -(5-deazapteroyl)-L-homocysteic acid (N5DHC), D,L-2-[N-(5-deazapteroyl)amino]-4-phosphobutanoic acid (N5DAPB), (6R,6S)-N R -(5-deaza-5,6,7,8-tetrahydropteroyl)-L-homocysteic acid (THFAC), (6R,6S)-5,8,10-trideaza-5,6,7,8-tetrahydropteroyl-L-glutamic acid (TDTHF), (2S)-2-[5-[N-(2-amino-4(3H)-oxopyrido-[2,3-d]pyrimidin-6-yl)methylamino]-2,3-dihydro-1(3H)-oxoisoindol-2-yl]aminopentane-1,5-dioic acid (PT648), and N Rpteroyl-L-ornithine (PT489) were previously described (29)(30)(31)(32)(33). N R -Pteroyl-L-histidine was synthesized as per Mao et al (34).…”

DNA and RNA Synthesis: Antifolates

“…Folate and MTX analogues 38a − 38c , with l -histidine in place of l -glutamate, have been synthesized as potential inhibitors of FPGS. No significant inhibition of the target enzyme by these compounds is observed …”

“…No significant inhibition of the target enzyme by these compounds is observed. 213 Partially restricted tricyclic antifolates 25d and 27e are reasonable substrates for FPGS but virtually inactive against CCRF-CEM human leukemia cells. The compounds and their congeners have also been evaluated in the NCI preclinical antitumor screening program.…”

Synthesis and dihydrofolate reductase inhibitory activity of 2-amino-6-(arylaminomethyl) thieno[2,3-d]pyrimidin-4(3H)-ones

“…Some of the known DHFR and TS inhibitors have several drawbacks, such as the doselimiting toxicities, low solubility, low specificity, short plasma half-life, low absorption and drug resistance development [2][3][4][5]. Therefore, development of novel antifolates remains relevant and has interest for various research groups [2,5,[6][7][8][9][10][11]. Thieno [2,3-d]pyrimidine heterocycle also attracts attention in that respect [12][13][14][15].…”