THe Synanon Foundation, a drug rehabilitation organization that has been embroiled in a controversy practically since the group attempted to establish East Coast headquarters in May at the Boston House apartments on Massachusetts Avenue NW, has left the city, knowledgeable sources said yesterday.

Herman Hochman, president of the Boston House Tenants Association, said "Friday was the last day for them, and as far we know, they are all out of here. We saw them moving their bedding and furniture out."

Leslie Scherr, an attorney who represented Synanon at an informal hearing with law enforcement officials here, said, "I believe there are no more Synanon people at the Boston House," Scherr would not say where the group has gone, nor could Synanon spokesmen be reached yesterday.

Two telephone numbers at Synanon offices at Boston House, 1711, Massachusetts Ave. NW. have been disconnected. Telephone operators gave a new number for the organization in Adams County, Pa.

Tensions between Synanon members and Boston House tenants began last spring when Synanon members indicated that they had entered into a tentative agreement to buy the apartment building and move into the seventh and eighth floors of the building. Some of the apartments, sources said, were made into offices.

The controversy heightened, however, when zoning official indicated that Synanon had violated city zoning laws for having offices without permits and when warrants were issued for Synanon Founder Charles Dederich and Howard Garfield, another Synanon member, for allegedly assaulting a Washington Post photographer.

At an informal hearing at the U.S. Attorney's office June 19, Synanon spokesmen indicated they would leave the Washington area by June 30 and that neither Garfield nor Dederich would come back into the area, sources reported at the time.

A source at the U.S. Attorney's office said yesterday that the warrants against Synanon members have not been dropped, but that "if they are indeed gone when the situation is reviewed, dropping the charges will just be a formality."