Douglas Marr of Keliher Real Estate has sold 132 Marlborough St. in the city's historic Back Bay for $3.9 million. The four story brick residential property was delivered vacant. New owners are gutting the 7 unit building and converting it into a single family with an in-law suite. The building is 6,400 s/f and has 3 parking spaces. The seller was Mainsail Management and the buyer is K Properties LLC.