When was Abu Ayyub al-Ansari martyred and buried in Constantinople, and was that after its conquest?

Abu Ayyub al-Ansari died during the attempt to conquer Constantinople in the year 52 AH. He requested to be buried at the furthest possible point within enemy territory. May Allah be pleased with him, he was buried in the heart of Constantinople (Istanbul), near the city wall, and his martyrdom occurred before the battle concluded.