Field Enterprise Inc., publisher of The Chicago Sun-Times, announced yesterday that it is taking over Cabot, Cabot & Forbes, a Boston-based real estate developer with operations in the Washington area.

Field, which is privately owned, said it has acquired "substantially all the stock" of Cabot, Cabot & Forbes, also a privately held company.

Cabot, Cabot & Forbes recently began construction of a $25 million office building on Pennsylvania Avenue between 12th and 13th Streets NW and said it expects to build other projects in the Washington area.

The take-over will substantially expand the real estate ventures of Field Enterprises, which is already in that business. Field owns several television stations, a paper company and a coal mine, in addition to the Sun-Times.

As announced by Field, the agreement will split up the two top officers of Cabot, Cabot and Forbes and separate that firm's real estate development business from some of its operating real estate holdings.

Field said Ferdinand Colloredo Mansfield will continue as president and chief executive officer of Cabot, Cabot & Forbes. But Gerald W. Blakeley Jr., the company's chairman and "certain of his associates" will retain the Ritz-Carlton Hotel in Boston the Ritz-Carlton in Chicago and Boston's Bay Tower restaurant.

The purchase price of the Cabot, Cabot & Forbes stock was not announced. Executives of both companies were unavailable after the announcement was made late yesterday.