Seeded players Hsieh Su-wei of Taiwan and Monica Niculescu of Romania were beaten Wednesday in the second round of the Strasbourg International.
The fourth-seeded Hsieh lost 6-4, 4-6, 7-6 (3) to Misaki Doi of Japan, and fifth-seeded Niculescu fell 4-6, 6-3, 6-2 to Anna Tatishvili of Georgia.
Last year's runner-up Alize Cornet downed Magda Linette 6-3, 6-4. At No. 3, the Frenchwoman is the highest remaining seeded player in the tournament.
Seventh-seeded Chanelle Scheepers of South Africa reached the quarterfinals by beating American Shelby Rogers 2-6, 6-3, 6-4.
Flavia Pennetta, Johanna Larsson, Eugenie Bouchard and Lucie Hradecka also advanced to the last eight.