In 1458 he ratified his brother's treaty with the Ottoman Sultan Mehmed II in Adrianople, and later the same year he conveyed his niece Theodora to her husband, Uzun Hassan of the Ak Koyunlu.

Ludovico's entourage proceeded to Venice, and either there or at their next stop, Florence, a new ambassador joined his following: Michael Alighieri, who said he was the envoy of Emperor David.

Bryer mentions a document dated 28 April 1470, wherein the protectors of the Bank of St. George at Caffa gave Michael Alighieri safe conduct which covered his children and subordinates.

"[8] William Miller, in his account of the Empire of Trebizond, likewise assumes Michael Alighieri was the legitimate representative, while ignoring the existence of the sketchy Ludovico da Bologna, who had been the primary advocate for a Christian league.

That answer came the summer of the next year: a fleet under his admiral Kasim Pasha sailed along the Black Sea coast of Anatolia towards Trebizond while he led an army from Bursa eastward towards the city.

[13] David was settled in Adrianople together with his family, and received the profits of estates in the Struma River valley, comprising an annual income of some 300,000 pieces of silver.

[17] Marginalia in a manuscript of the gospels belonging to the commercial school at Chalke provide us with the date of the imprisonment of the five men: Saturday, 26 March 1463.

[18] This date is verified by another manuscript containing the Histories of Thucydides, currently held by the London Medical Society, which also adds that David's sons had converted to Islam under the influence of members of the Kabasitanoi, who had done so out of hunger.

Their execution was confirmed by a letter written by the Patriarch Sophronios I, who wrote that David "with his three sons" was killed "a few days" after his arrival in Constantinople.

Later she was married to Zaganos Pasha[20] according to some sources she was killed by her husband because she did not want to convert, while according to others, she remarried Elvanbeyzade Sinan Bey after becoming widowed or divorced.

Spandounes also writes that the widowed Empress Helena Kantakouzene was heavily fined by the Sultan for burying her husband and her sons, and spent the rest of her life in poverty.

Her youngest son, George, was raised as a Muslim, but when he was later allowed to visit Uzun Hasan in Persia, he fled from the court to his sister in Georgia, where he reverted to Christianity and married a Georgian princess.

[24] David and the fall of Trebizond are portrayed in Dorothy Dunnett's novel The Spring of the Ram, second book in her House of Niccolo series.

David appears as a minor character in Lawrence Schoonover's novel The Burnished Blade, where he is portrayed as an adventurous but diplomatically astute young man.