Analogues of Methotrexate in Rheumatoid Arthritis. 1. Effects of 10-Deazaaminopterin Analogues on Type II Collagen-Induced Arthritis in Mice

Carbonation of the dianions (LDA) of 5-methylthiophene-2-carboxylic, 2-methylpyridine-5-carboxylic, and 3-methylpyridine-6-carboxylic acids provided the respective carboxy heteroarylacetic acids. The crude diacids were directly esterified in MeOH−HCl to afford the diesters. Alkylation of the sodio anions with ethyl iodide yielded the appropriate α-ethyl diesters. The anions of the various diester substrates were then alkylated by 2,4-diamino-6-(bromomethyl)pteridine followed by ester saponification at room temperature to afford the respective 2,4-diamino-4-deoxy-10-carboxy-10-deazapteroic acids. The 10-carboxyl group was readily decarboxylated by heating in DMSO at temperatures of 110−135 °C to give the diamino 10-deaza heteropteroic acid intermediates. Coupling with diethyl l-glutamate followed by ester hydrolysis afforded the target aminopterins. The analogues were evaluated for antiinflammatory effect in the mouse type II collagen model. The thiophene analogue of 10-ethyl-10-deazaaminopterin was found to be an effective inhibitor in terms of reduced visual evidence of inflammation and swelling as determined by caliper measurement.