gave a 32 yield of 5 deazaaminopterin diethyl ester saponification of the ester groups in a mixture of dimethyl sulfoxide water at ambient temperature gave an 87 yield of 5 deazaaminopterin ii r h methylation of the latter compound was accomplished by treatment of ii r h with formaldehyde and sodium cyanoborohydride in aqueous solution at ph 6 4 to give an 85 yield of 5 deazamethotrexate ii r ch 3 the structure of ii r ch 3 was established as described hereinafter in example 8c by oxidation with alkaline potassium permanganate to give the previously prepared 2 amino 4 3h oxopyrido 2 3 d pyrimidine 6 carboxylic acid viii which indicated that methylation had occurred either on the 4 or 10 amino group methylation of the 4 amino group was eliminated from consideration by alkaline hydrolysis of the 4 amino group to give 5 deaza 10 methylfolic acid i r ch 3 the preferred route for the preparation of i r h involves the hydrolysis of 5 deazaaminopterin diethyl ester vii r h r 1 c 2 h 5 in aqueous sodium hydroxide at reflux temperature which resulted in replacement of the 4 amino group as well as hydrolysis of the ester functions to give a 79 yield of 5 deazafolic acid i r h methylation of the compound of formula i r h with formaldehyde.