Carter Vincent Boehm, a Northern Virginia real estate broker indicted on federal drug charges and linked to the cocaine investigation of developer Mark R. Vogel, pleaded guilty on Monday to a single count of obstruction of justice in federal court in Charlottesville.

More serious charges of conspiracy to possess cocaine with the intent to distribute were dropped against Boehm, 41, and a co-defendant, Robert Gregory Brownwell, 30, of McLean, said Boehm's attorney, Nicholas Balland. Brownell also pleaded guilty to obstruction of justice.

Prosecutors agreed to recommend probation for both men in exchange for the guilty pleas, Balland said. The obstruction of justice charge carries possible maximum penalties of five years in prison and $250,000 in fines.

Prosecutors said on Monday that Drug Enforcement Administration agents began an investigation of Boehm after he gave them untruthful information during a 1989 inquiry of drug trafficking in the Washington suburbs. Sources confirmed yesterday that the 1989 investigation focused upon Vogel, a well-known Prince George's County developer.

Vogel, who was arrested last September during a traffic stop on Georgetown Pike near Boehm's Great Falls home, pleaded guilty in November to possession of four grams of cocaine.

Vogel had dined with Boehm and two women at a District restaurant the night of his arrest and later told federal agents that he was en route to Boehm's house to use the cocaine, according to federal affidavits. Federal affidavits also allege that Boehm carried cocaine on board Vogel's corporate helicopter on trips to Atlantic City.

Balland declined to say yesterday whether Boehm had cooperated with federal authorities in their probe of Vogel.

"The fact that the government dismissed the lead count of the indictment, conspiracy to possess cocaine with the intent to distribute, on their own motion indicates that Mr. Boehm was never a drug dealer," Balland said. "If that wasn't the case, they wouldn't have dropped the charges."

Boehm, Brownell and two other men, Edward P. Stuart and Robert Brian Leith, were indicted in June in connection with a scheme to trade machine guns for a kilogram of cocaine. Boehm pleaded guilty to charges that he tried to persuade a fellow defendant to alter his testimony.

Stuart, 27, of Sterling, faces up to 45 years in prison after pleading guilty to attempting to purchase cocaine from a federal agent and to carrying a gun while making the deal.

The charges against the four men arose from the April arrest of Stuart and Leith, of Fairfax. Leith, who was not prosecuted in exchange for his cooperation in the case, and Stuart had tried to buy cocaine from undercover federal agents posing as drug dealers, according to the indictment.