Synthesis and structure confirmation of 7‐ester‐8‐aminomethylene‐substituted baicalein derivatives

Twelve baicalein derivatives, derivatized with 7‐ester and 8‐aminomethylene groups, were synthesized as cyclin‐dependent kinase 1 (CDK1) inhibitors, by the addition of one of four secondary amines to C‐8, using the Mannich reaction, followed by mono‐esterification with one of three carboxylic acids. Analysis by 1H‐, 13C‐NMR, and HMBC spectra, as well as a chemical test, confirmed that the esterification occurred at the 7‐phenolic hydroxyl position of baicalein but not at the 5‐ or 6‐positions. 7‐ester‐8‐aminomethylene‐substituted baicalein derivatives were successfully synthesized by a Mannich reaction, followed by esterification. Combination of the 1H, 13C‐NMR, HMBC data, and strontium chloride reactivity results, the structures of the final compounds could be confirmed.