Regioselective addition of Grignard reagents to -acylpyrazinium salts: synthesis of substituted 1,2-dihydropyrazines and Δ-2-oxopiperazines.

The regioselective addition of Grignard reagents to mono- and disubstituted -acylpyrazinium salts affording substituted 1,2-dihydropyrazines in modest to excellent yields (45-100%) is described. Under acidic conditions, these 1,2-dihydropyrazines can be converted to substituted Δ-2-oxopiperazines providing a simple and efficient approach towards their preparation.

Discovery and characterization of an iminocoumarin scaffold as an inhibitor of MEKK2 (MAP3K2).

The kinase MEKK2 (MAP3K2) activates the MEK5/ERK5 cell signaling pathway and may play an important role in tumor growth and metastasis. Thus, MEKK2 may represent a novel kinase target for cancer. In order to identify inhibitors of MEKK2, we screened a library of compounds using a high throughput MEKK2 intrinsic ATPase enzyme assay.

Regioselective reduction of 3-substituted N-acylpyrazinium salts toward the synthesis of 1,2-dihydropyrazines.

The regioselective reduction of 3-substituted N-acylpyrazinium salts with n-Bu(3)SnH has been developed for the synthesis of 3-substituted 1,2-dihydropyrazines in yields of 56-94%. Substitution of the pyrazinium salts with electron-donating groups favors the formation of the 1,2-isomers as a result of their better stability over the 1,6-isomers. Under mild acidic conditions, 3-methoxy substituted 1,2-dihydropyrazine was easily hydrolyzed in excellent yield to Δ(5)-2-oxopiperazine.