Despite Holly Winterburn’s career-high 23 points, the Lions were never in the lead during the game.
After defeating Umana Reyer Venice in March, the London Lions advanced to the European final, becoming the first basketball team from Britain.
On April 10, at London’s Copper Box Arena, they will try to overcome their seven-point disadvantage in the second leg of the match.
With 20 points, Dana Evans led the charge for three-time Turkish league champions Besiktas, while Jovana Nogic chipped in with 18 points for the hosts Aziz Akkaya.
Karlie Samuelson (16) and Katsiaryna Snytsina (10) also scored in double figures for the Lions, who trailed by 18 points after 12 consecutive points.
