title: Synthesis and biological activity of the 2-desamino and 2-desamino-2-methyl analogues of aminopterin and methotrexate.
abstract: The previously undescribed 2-desamino and 2-desamino-2-methyl analogues of aminopterin (AMT) and methotrexate (MTX) were synthesized from 2-amino-5-(chloromethyl)pyrazine-3-carbonitrile. The AMT analogues were obtained via a three-step sequence consisting of condensation with di-tert-butyl N-(4-aminobenzoyl)-L-glutamate, heating with formamidine or acetamidine acetate, and mild acidolysis with trifluoroacetic acid. The MTX analogues were prepared similarly, except that 2-amino-5-(chloromethyl)pyrazine-3-carbonitrile was condensed with 4-(N-methylamino)benzoic acid and the resulting product was annulated with formamidine or acetamidine acetate to obtain the 2-desamino and 2-desamino-2-methyl analogues, respectively, of 4-amino-4-deoxy-N10-methylpteroic acid. Condensation with di-tert-butyl L-glutamate in the presence of diethyl phosphorocyanidate followed by ester cleavage with trifluoroacetic acid was then carried out. Retention of the L configuration in the glutamate moiety during this synthesis was demonstrated by rapid and essentially complete hydrolysis with carboxypeptidase G1 under conditions that likewise cleaved the L enantiomer of MTX but left the D enantiomer unaffected. The 2-desamino and 2-desamino-2-methyl analogues of AMT and MTX inhibited the growth of tumor cells, but were very poor inhibitors of dihydrofolate reductase (DHFR). These unexpected results suggested that activity in intact cells was due to metabolism of the 2-desamino compounds to polyglutamates.
authors.affiliation: Dana-Farber Cancer Institute, Boston, Massachusetts.
authors.forename: A
authors.initials: A
authors.lastname: Rosowsky
authors.forename: R A
authors.initials: RA
authors.lastname: Forsch
authors.forename: R G
authors.initials: RG
authors.lastname: Moran
authors.forename: J H
authors.initials: JH
authors.lastname: Freisheim
mesh_terms: D000630:Aminopterin / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004261:DNA Replication / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D005493:Folic Acid Antagonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007202:Indicators and Reagents; D008727:Methotrexate / Q000031:analogs & derivatives* / Q000494:pharmacology; D015394:Molecular Structure; D013329:Structure-Activity Relationship
chemical_list: D000964:Antimetabolites, Antineoplastic; D005493:Folic Acid Antagonists; D007202:Indicators and Reagents; D000630:Aminopterin; D008727:Methotrexate