Answer:
Went the Ottomans conquered Constantinople in 1453, and renamed the city "Istanbul", the became the rulers of most of the Eastern Mediterranean, and the lands between Europe and Persia (and between Europe and East Asia).
Step-by-step explanation:
In other words, the Ottoman Empire became the middle man between Europe an Asia, and this gave them a level of power that made Europeans uncomfortable (besides making trade more expensive).
This was actually the main motivation behind Christopher Columbus Voyages: he wanted to find a new route between Europe and Asia, in order to bypass the Ottoman controlled lands. He never thought that he would encounter the whole new continent of the Americas.