Born in the Soviet Union in 1966, Felix H. Sater immigrated with his family to Brighton Beach when he was 8 years old. At 24 he was a successful Wall Street broker, at 27 he was in prison after a bloody bar fight, and at 32 he was accused of conspiring with the Mafia to launder money and defraud investors. Along the way he became embroiled in a plan to buy antiaircraft missiles on the black market for the Central Intelligence Agency in either Russia or Afghanistan, depending on which of his former associates is telling the story. But in recent years Mr. Sater has resurfaced with a slightly different name and a new business card identifying him as a real estate executive based on Fifth Avenue. And although he may not be a household name, one of the people he is doing business with is: Donald J. Trump. Mr. Sater — who now goes by the name Satter — has been jetting to Denver, Phoenix, Fort Lauderdale, Fla., and elsewhere since 2003, promoting potential projects in partnership with Mr. Trump and others. In New York, the company Mr. Sater works for, Bayrock Group, is a partner in the Trump SoHo, a sleek, 46-story glass tower condominium hotel under construction on a newly fashionable section of Spring Street. A federal complaint brought against him in a 1998 money laundering and stock manipulation case was filed in secret and remains under seal. A subsequent indictment in March 2000 stemming from the same investigation described Mr. Sater as an “unindicted co-conspirator” and a key figure in a $40 million scheme involving 19 stockbrokers and organized crime figures from four Mafia families. The indictment asserted that Mr. Sater helped create fraudulent stock brokerages that were used to defraud investors and launder money. Mr. Sater and his lawyer, Judd Burstein, repeatedly refused to discuss in detail his role in the stock scam. But a onetime friend, Gennady Klotsman, who is known as Gene and who was accused with Mr. Sater as a co-conspirator, contends that they both pleaded guilty in 1998, and that Mr. Sater began cooperating with the authorities. Prosecutors are unwilling to discuss either the 1998 complaint or the 2000 indictment. Mr. Sater was born in the Soviet Union, the son of Rachel and Mikhail Sater, according to public records, court testimony and the federal indictment. He has said his parents, who are Jewish, moved first to Israel, then to Baltimore and finally to New York in the early 1970s to escape “religious persecution.” Mr. Sater was born Haim Felix Sater, but he once testified in court that he “Americanized” his name to Felix Henry Sater in the early 1990s. Mr. Sater took classes at Pace University but dropped out at 18 to work at Bear Stearns. Like Mr. Klotsman, he rose quickly, moving from firm to firm selling stock. Mr. Sater, Mr. Klotsman, Salvatore Lauria and their partners gained control in 1993 of White Rock Partners, which later changed its name to State Street Capital Markets. The trio would secretly gain control of large blocks of stock and warrants in four companies through offshore accounts, the indictment said. In an illegal “pump and dump” scheme, they would inflate the value of the shares through under-the-table payoffs to brokers who sold the securities to unsuspecting investors by spreading false information about the companies. At the same time, Mr. Sater, Mr. Lauria and others sought protection and help from members of the Mafia in resolving disputes with “pump and dump” firms operated by other organized crime groups. In 1995, for instance, Edward Garafola, a soldier in the Gambino crime family, sought to extort money from Mr. Sater. Mr. Sater, in turn, got Ernest Montevecchi, a soldier in the Genovese crime family, to persuade Mr. Garafola to back off, according to the indictment. Mr. Sater said he joined Bayrock in 2003 at the urging of the company’s founder, Mr. Arif. A neighbor of Mr. Sater’s in Sands Point, on Long Island, Mr. Arif is a former economist for the Soviet government who built a chain of five luxury hotels in Turkey and Kazakhstan after the collapse of the Soviet Union.