Lawyers at Oppenheimer Wolff & Donnelly's Palo Alto office were informed of its closure just days before the firm pulled out of Silicon Valley.
According to a spokesman at Oppenheimer, the firm told its 40-lawyer office that it would close its doors "a few days" before making an official announcement on 30 May.
The move followed the revelation that 28 of its lawyers were defecting to Dechert, leaving the remaining mainly corporate lawyers with a very short space of time to find new jobs.
The mass defection, led by intellectual property partners Michael Kalkstein and Chris Graham, threw the planned sale of the entire Palo Alto office into doubt, prompting the decision to close it down.
In a statement, the firm said: "Those employees who have not accepted an offer from Dechert or another law firm have been terminated and told that Oppenheimer's Palo Alto office will close, effective 30 May 2003."
At the same time, Oppenheimer also announced that it would shut its Orange County office by mid-July, although it intends to keep a small branch in Santa Monica.
As well as Palo Alto and Orange County, Oppenheimer has pulled the plug on its presence in New York and Los Angeles, leaving just a main office in Minneapolis.
The firm intends to keep its branches in Brussels, Geneva and Paris.
Sources had hinted that Dechert, as well as taking the group of lawyers, had been contemplating subleasing Oppenheimer's space at 1400 Page Mill Road.
However, Dechert has taken space in a different building in the same area, leaving Oppenheimer to negotiate its exit from its expensive lease on 55,000 sq ft of space, rented at the height of the dotcom boom.
The firm said: "The parties are still negotiating a possible agreement regarding the Palo Alto office space lease, its furniture and equipment."