A series of I-[[[5-(substituted phenyl)-2-oxazolyl] methylene] amino]-2, 4-imidazolidinediones (6a-t) was synthesized, and the compounds were evaluated for direct skeletal muscle inhibition in the pithed rat gastrocnemius muscle preparation. The correctness of structural assignment of the new series was verified by alternate, unequivocal synthesis of one representative structure (6f). The phenyloxazoles 6d, 6g, Sj, 6k, and 61 exhibited ...