These excerpts come from Syridon Lambros's publication of the Ecthesis Chronicon.

In those times, they brought the emperor a wife from Trebizond, Maria Cantacuzena, the granddaughter of the protostrator since he had his daughter as a wife for the protovestarius of the emperor of Trebizond1. Maria was extremely beautiful and the like of which could not be found in those times. The emperor married her and loved her extravagantly for her beauty and her intelligence.

1. Maria as her contemporaries tell us was actually the daughter of the emperor of Trebizond Alexius Comnenus. Is this confusion on the historian’s part or some secret knowledge? What is curious about this is that we are informed by Pseudo-Chalcodylus [pg. 146] that the empress Theodora Comnena had intercourse with the protovestarius.

While Joseph was patriarch, the lord sultan Mehmed marched out against Trebizond with a numerous land force and innumerable number by sea. The emperor at that time was lord David, who hailed from the Comnene family. When he saw the multitudinous coming and the multitude of this force, he was not able to do anything about and so he unwillingly submitted. He did make some requests, one of which was that he [the sultan] would take as his wife his daughter, and so he promised to marry her. This emperor also had another daughter, the despoina Hatun, who had gone to Uzun Hasan in Tabriz and had three sons with him. The emperor had hoped of getting aid from him, but he was unable to help him on the whole because he feared lest he should be campaigned against. Because of this fear, he sent as his ambassador his mother along with many gifts to the lord whom she met en route and told him thus: “Let it be known to your majesty that I am not your opponent…He received her warmly and in a friendly manner, before sending her back home. The poor emperor also asked he be given a place as alimony for his family, which acquiesced to, and he sent him the keys to the city. He had ruled this province from Aminsoun until the borders of Iberia without any difficulty until the war. They then split up the people of Trebizond into three parts. One of these parts he and his magnates took, the other he brought to the city as sergunides [settlers?], while the other part he left in the city to live no within, but without its walls. As for the emperor and all of his officials, he loaded them onto the boats and brought them to Constantinople, including Kabazetes [Kabazites] and all his family, the grand mesazon Altamurius, and the philosopher Ameroutzes [Amoiroutzes] the protobestarios. The protobestarios was the grandson of Yagares just like the pasha Mahmud by another of Yagares’s daughters in Serbia, so they were first cousins. By the treachery and deception of the protobestarios, the lord got into Trebizond. It was he who persuaded the poor emperor and he submitted since the emperor was indolent, unmanly, and unfit for rule. The protobestarios met with great honor from the lord and pasha since he was handsome, manly in the size of his body and fitness. As an archer he had no equal in the sultan’s army. As for Amirutzes son’s he brought them into the Seraglio and later made Amirutzes into an Ishmaelite. As for the emperor, he gave him as an alimony some land next to Serres and as for his daughter who he had promised to marry, he did not marry her but gave he to his hotzia to get her to renounce the faith of Christ, but he was unable to dissuade her and so released her. She had food until the end of her life. Later, however, when he came into conflict with Uzun Hasan, as he was about to march off against him, he killed the poor emperor. We do not know what the reason was.

In those times there were young well born men within the Seraglio from the City and Trebizond, one of whom was Amoiroutzes’s son Mehmed bey who was very learned in Greek and Arabic and by order of the lord [sultan] translated our books into the Arabic language very accurately.

A little time later, he marched off to Persia against Shakh Ishmael [the sheikh Ishmael]. The sheikh Ishmael was the son of sheikh Khaytar, the sheikh Khaytar was the son of sheikh Djunayd all of them descended from Ali, who was the son-in-law of Mehmed their prophet. They were seytides with numerous children, lands, and boundless people. His grandfather, the sheikh Djunayd, while Trebizond was still around, and a sudden plague took place and the emperor and all his officials fled to the coast, the sheikh Djunayd fell on them suddenly with a great host made a great massacre killing many of their handsomest and manliest. They were not at arms, but at pleasures and so he seized their property, arms, and horses. The sultan Mehmed on learning that a dervish had been so victorious; he marched off and took Trebizond. The sheikh Djunayd died leaving his sheikdom to his son the sheikh Khaytar. He then when was asked by Rustam bey, the son of the Uzun Hasan and the daughter of the emperor David, the despoina Hatoun, who was ruler in Persia, to give him the right [permission?] to march off and enslave the districts of Trebizond. Since he did not give him the right [permission?], he went to war with him and defeated him cutting off sheik Khaytar’s head. Sheikh Khaytar had a son by the daughter of Uzun Hasan: the sheikh Ishmael.