Teen sensation L Devendro Singh and Commonwealth Games gold-medalist Manoj Kumar have booked their Olympic berths by advancing to the World Boxing Championships' quarter-finals. At Baku, Azerbaijan today, while Manoj rallied to defeat China's Qing Hu 17-15 in the 64 kg category, 19-year-old Devendro continued his giant-killing spree by beating seventh seed Carlos Quipo of Ecuador 18-12 in the 49 kg division.The duo has become the first lot of Indian boxers to qualify for the London Olympics. In the 81 kg category, there was disappointment for India as Asian Games silver-medalist and 12th seed Dinesh Kumar bowed out with a 7-16 loss to CWG gold-medalist Damien Hooper of Australia.Today, two other Indian pugilists Jai Bhagwan and Vikas Krishan will box in their respective categories for a place in the Olympics.