General procedure for the synthesis of 6-hydroxy-7-methoxyquinazolin-4-one from 6,7-dimethoxyquinazolin-4-one:
1. 3.06 g of 6,7-dimethoxyquinazolin-4-one was dissolved in 20 mL of methanesulfonic acid.
2. 2.66 g of L-methionine was added to the above solution and the reaction was stirred at 100 °C for 22 hours.
3. Upon completion of the reaction, ice was added to the reaction mixture and neutralized with 40% aqueous sodium hydroxide solution to pH neutral to promote crystallization of the product.
4. The solid product was collected by filtration under reduced pressure, washed with water and subsequently air dried to afford 6-hydroxy-7-methoxyquinazolin-4-one (2.67 g, 94% yield).
Product characterization data: 1H-NMR (300MHz, DMSO-d6) δ 11.94 (s, 1H), 9.81 (s, 1H), 7.92 (d, J=Hz, 1H), 7.39 (s, 1H), 7.11 (s, 1H), 3.91 (s, 3H).
