Demetrios is first attested in 1345, already holding the senior military rank of megas stratopedarches, during the siege of Serres by the forces of the Serbian ruler Stephen Dushan. A large part of the city's population, under Manuel Asen, wanted to surrender the city to the Serbs, while Tzamplakon led the loyalist faction. After the city's fall, he withdrew to Christoupolis, and is still attested in the 1360s. He donated his extensive lands in Macedonia to the Vatopedi Monastery of Mount Athos.
