Grubb & Ellis Co. has assisted in selling three separate commercial properties in Boston and Billerica.

A 19,600-square-foot, four-story retail property at 13-15 Winter St. in Boston’s Downtown Crossing sold for $3.2 million.

Grubb & Ellis’ Anthony Biette, vice president, Mike Edward, executive vice president and managing director, and Phil Giunta, executive vice president, led the team representing the Roxbury Operating Trust in the transaction, valued at $163 per square foot.

The Boston Capital Markets Group also marketed and sold 407 Washington St., another retail property in Boston’s Downtown Crossing district. The 21,956-square-foot building is suited for retail/restaurant with office or residential use above. Biette, Giunta and Paul Stanislas, vice president, retail, led the team representing the 407 Washington Street Trust in the transaction, valued at approximately $3 million, or $134 per square foot.

Grubb & Ellis was also the exclusive agent for the marketing and sale of 900 Middlesex Turnpike, Building 5, in Billerica. At 46,402 square feet, Building 5 is one of six buildings totaling 440,000 square feet in the suburban Boston industrial park. Biette worked directly with leasing specialists Tom Aitken, senior vice president, and Tyler Ewing, senior associate, office, led the team representing NationWide-Middlesex Tech V LLC in the transaction, valued at approximately $1.3 million, or $28 per square foot.

The Grubb & Ellis Capital Markets is led by Biette and Giunta, with direct support from Jory Crowell, senior financial analyst, and Ann Newman, account coordinator.