title: Synthesis and antifolate evaluation of 10-ethyl-5-methyl-5,10- dideazaaminopterin and an alternative synthesis of 10-ethyl-10- deazaaminopterin (edatrexate).
abstract: Previous findings suggesting that 5,10-dialkyl-substituted derivatives of 5,10-dideazaaminopterin warranted study as potential antifolates prompted synthesis of 10-ethyl-5-methyl-5,10- dideazaaminopterin (12a). The key step in the synthetic route to 12a was Wittig condensation of the tributylphosphorane derived from 6-(bromomethyl)-2,4-diamino-5-methylpyrido[2,3-d]pyrimidine (7a) with methyl 4-propionylbenzoate. Reaction conditions for the Wittig condensation were developed using the tributylphosphorane prepared from 6-(bromomethyl)-2,4-pteridinediamine (7b) as a model. Each of the respective Wittig products 8a and 8b was obtained in 75-80% yield. Hydrogenation of 8a and 8b at their 9,10-double bond afforded 4-amino-4-deoxy-10-ethyl-5-methyl-5,10-dideazapteroic acid methyl ester (9a) and 4-amino-4-deoxy-10-ethyl-10-deazapteroic acid methyl ester (9b). This route to 9b intersects reported synthetic approaches leading to 10-ethyl-10-deazaaminopterin (10-EDAM, edatrexate), an agent now in advanced clinical trials. Thus the Wittig approach affords an alternative synthetic route to 10-EDAM. Remaining steps were ester hydrolysis of 9a,b to give carboxylic acids 10a,b followed by standard peptide coupling with diethyl L-glutamate to produce diethyl esters 11a,b, which on hydrolysis gave 12a and 10-EDAM (12b), respectively. The relative influx of 12a was enhanced about 3.2-fold over MTX, but as an inhibitor of dihydrofolate reductase (DHFR) from L1210 cells and in the inhibition of L1210 cell growth in vitro, this compound was approximately 20-fold less effective than MTX (DHFR inhibition, Ki = 4.82 +/- 0.60 pM for MTX, 100 pM for 12a; cell growth, IC50 = 3.4 +/- 1.0 nM for MTX, 65 +/- 18 nM for 12a).
authors.affiliation: Kettering-Meyer Laboratory, Southern Research Institute, Birmingham, Alabama 35255.
authors.forename: J R
authors.initials: JR
authors.lastname: Piper
authors.forename: C A
authors.initials: CA
authors.lastname: Johnson
authors.forename: G M
authors.initials: GM
authors.lastname: Otter
authors.forename: F M
authors.initials: FM
authors.lastname: Sirotnak
mesh_terms: D000630:Aminopterin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000494:pharmacology; D005493:Folic Acid Antagonists; D007939:Leukemia L1210 / Q000188:drug therapy / Q000201:enzymology; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D005493:Folic Acid Antagonists; C076122:10-ethyl-5-methyl-5,10-dideazaaminopterin; C040210:edatrexate; D000630:Aminopterin