Ukrainian Taras Shelestyuk and Great Britain's Freddie Evans had bouts go to countbacks Tuesday, but both won to move into the semifinals of the men's welterweight draw.
Meanwhile, the United States is again without a boxer in the men's competition after Errol Spence lost.
The top-seeded Shelestyuk, the reigning world champion, fought France's Alexis Vastine to an 18-18 draw but advanced on the strength of his point total from all three rounds.
Evans did the same against Canada's Custio Clayton, and now faces Shelestyuk on Friday.
On the other side of the quarterfinal bracket, Spence was knocked out of the competition by Russian Andrey Zamkovoy, a 16-11 winner. The American had been awarded a berth into the quarterfinals after his appeal of a second-round loss was accepted.
Zamkovoy moved on to face No. 2 seed Serik Sapiyev, who routed Venezuela's Gabriel Maestre Perez on Tuesday.
In men's flyweight action, Russian Misha Aloian eased into the semifinals and will fight Tugstsogt Nyambayar of Mongolia. Aloian is the top seed in the draw.
Great Britain's Andrew Selby, the No. 2 seed, lost to Cuban Robeisy Ramirez Carrazana. Ireland's Michael Conlan, the sixth seed, advanced to fight Ramirez Carrazana.