BOSTON— The historic Tremont Boston Hotel here will soon be converted into the Boston Tremont Courtyard by Marriott hotel by new owner Highland Hospitality Corporation. Highland bought the asset from Wyndham International, Inc. in August. Through a definitive, long-term management agreement that Highland signed with Marriott International, Inc., Marriott will begin managing the property on Oct. 16. The conversion will begin in early 2005. Highland acquired the 322-room Tremont along with three other hotels from Wyndham.