MC Real Estate Partners LLC, in partnership with an undisclosed capital source, has purchased a 76,000-square-foot historic office building located at 110 Chauncy St. in downtown Boston. The property was originally built in the 1890s and will serve as the new headquarters for global design firm Sasaki, which has signed a 64,000-square-foot lease. MC Real Estate will work with Sasaki to redesign and renovate the space, which will house approximately 250 employees.