Americans Marlen Esparaza and Claressa Shields ensured they would win medals Monday in the Olympic women\'s boxing tournament. Esparaza won her quarterfinal bout in the flyweight division over Karlha Magliocco of Venezuela and will meet top-seeded Ren Cancun of China in the semis. Shields outlasted Sweden\'s Anna Laurell to set up a semifinal meeting with Marina Volnova of Kazakhstan, who ousted No. 1 seed Savannah Marshall of Britain in the middleweight class. Semifinal losers in Olympic boxing receive a bronze medal. A dozen male boxers also clinched medals Monday in the lightweight, middleweight, and super-heavyweight quarterfinals. Cuba\'s Yasnier Toledo Lopez defeated Gani Zhalauov of Kazakhstan in one of the top bouts of the day, scoring a 19-11 decision in the lightweight class. Toledo Lopez will face Ukraine\'s Vasyl Lomanchenko in the semifinals Friday. The other lightweight semifinal will send Evaldes Petrauskas of Lithuania against South Korea\'s Soonchul Han. Britain\'s Anthony Ogogo led the way into the middleweight semifinals with a 15-4 whipping of Germany\'s Stefan Hartel. Ogogo\'s semifinal opponent will be Esquiva Falcao Florentino of Brazil. Abbos Atoev of Uzbekistan will face Ryota Murata of Japan in the other semifinal. Quarterfinal action in the super-heavyweight division set up semifinal bouts in which Magomedrasul Medzhidov of Azberbaijan will meet Italy\'s Roberto Cammarelle and Ivan Dychko of Kazakhstan will fight Anthony Joshua of Britain.