• Houghton, C., et al.: Biochem. J., 130, 879 (1964)
• Ensign, J., et al.: Biol. Chem., 239, 2285 (1964)
• Dilithiation can be effected with LDA, allowing substitution at the 6-methyl group, as, for example carboxylation in the synthesis of methotrexate analogues: J. Med. Chem., 40, 370 (1997).