Methods of making monomethyl fumarate, which can then also be used in methods of making prodrugs of monomethyl fumarate, are disclosed. Monomethyl fumarate and prodrugs of monomethyl fumarate are useful for treating neurodegenerative, inflammatory, and autoimmune diseases including multiple sclerosis, psoriasis, irritable bowel disorder, ulcerative colitis, arthritis, chronic obstructive pulmonary disease, asthma, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis.