Lawyers for millionaire developer Dominic F. Antonelli Jr. urged the U.S. Court of Appeals here yesterday to uphold a federal judge's order granting a new trial for Antonelli and former D.C. mayoral aide Joseph P. Yeldell.

In a 55-page legal pleading, Antonelli's chief defense alwyer, Edward Bennett Williams, asked the Ocurt of Appeals to reject arguments made previously by federal prosecutors, who have petitioned the appeals court to reinstate guilty verdicts that had been returned against Antonelli last year by a federal jury.

Williams termed the prosecutors' legal move "wholly inappropriate" and literally unprecedented." At several points, he accused the prosecutors of "sandbagging" the U.S. District Court judge, who issued the order for a new trial.

Antonelli, a real estate investor and parking company owner, and Yeldell, who has remained on unpaid leave from his most recent D.C. governement job as a top aide to former Mayor Walter E. Washington, were convicted of bribery and conspiracy charges in October. Antonelli was accused of helping to arrange loans, including a secret $33,000 personal loan, to Yeldell in exchange for Yeldell's help in securing an allegedly lucrative D.C. government lease for a partenership controlled by Antonelli.

On Nov. 27, Judge Gerhard A. Gesell, who had presided at the two men's trial, ordered the guilty verdicts set aside and granted Antonelli and Yeldell a new trial. A key factor in Gesell's order was a surprise disclosure that one juror had failed to divulge that she once had a small checking account at Madison National Bank -- a bank that figured centrally in the trial.

Federal proslecutors repsoned in December by peitioning for what is known as a writ of mandamus, asking the Court of Appeals to voerturn Gesell's new-trial order and reaffirm the guilty verdicts. Yesterday was the deadline set by the appeals court ofr reponses to the prosecutors' petition. Although Antonelli's lawyers filed a response, none had been received by late afternoon from Yeldell's lawyer, John A. Shorter Jr., according to court officials. Judge Gesell did not file a response.

How Quickly the appeals court will act on the prosecurtors' petition is uncertain. The court may rule immediately or may seek additional oral arguments or written memoranda. A second trial on the charges against Antonelli and Yeldell initially had been scheduled by Judge Gesell for late next month, but the starting date was canceled after prosecutors petitioned the Court of Appeals, and no new trial date has been set.

Wiliams, Antonelli's lawyer, contended yesterday that overturning Gesell's order would be unwarranted, in part, becuase "the government's interests are adequately protected by a retrial before a fair and impartial jury."