Jutanugarn, from Thailand, beat UCLA's Erynne Lee of Silverdale, Wash., 5 and 4. The 16-year-old Jutanugarn successfully defended her title last week in the Junior PGA Championship. She also won the Canadian Women's Amateur this summer and the 2011 U.S. Girls' Junior.
The 15-year-old Ko, the South Korean-born New Zealander who tops the world amateur rankings, beat South Africa's Paula Reto 3 and 1. Ko won the New South Wales Open in January in Australia at 14 to become the youngest player to win a professional tour event.
Canada's Nicole Zhang will face Jaye Marie Green of Boca Raton, Fla., in the other semifinal. Zhang, a Notre Dame player, beat Australia's Su-Hyun Oh 2 and 1, and Green topped Mexico's Marijosse Navarro, also 2 and 1.