Buenos Aires (Argentina), Aug 10 : Teenager Valentin Barco converted the decisive spot-kick as Argentine giants Boca Juniors advanced to the Copa Libertadores quarterfinals by beating Uruguay's Nacional on penalties. After a goalless draw in the first leg, Boca made an ideal start to their return fixture when Miguel Merentiel scored in the 12th minute at La Bombonera on Wednesday, Xinhua reported. Alfonso Trezza equalized shortly after before Luis Advincula restored Boca's advantage just after halftime. Ignacio Ramirez put the visitors back on level terms thanks to Ignacio Ramirez's 75th-minute strike, forcing the match into a penalty shootout. Ramirez and Daniel Bocanegra both squandered their spot-kicks for the Montevideo outfit while Boca's only blemish in the shootout was a miss from Guillermo Fernandez. Nineteen-year-old defender Barco then showed poise beyond his years by calmly slotting home the winning penalty and earning his team a place in the competition's last eight. In other Copa Libertadores fixtures on Wednesday, Palmeiras advanced after overcoming Brazilian rivals Athletico Paranaense and Deportivo Pereira progressed by edging past Independiente del Valle. /IANS