Methods for the synthesis of 5-carboxy-6-methyluracil (9), which is expected to be useful as an intermediate for the preparation of sparsomycin analogs, were investigated. A new route that leads to 9 from cyanoacetylurea (5) via 2-cyano-3-oxobutanoylurea (6a), 5-cyano-6-methyluracil (7a), and 5-carbamoyl-6-methyluracil (8), was developed. The total yield from 5 to 9 was 20.7%.
