A Boston man allegedly was sexually assaulting an unconscious woman early Sunday morning when State Police appeared near the Community Boating area on the Esplanade and forced him to stop his attack, according to a State Police report filed in court today.

Joseph Barthel, 49, pleaded not guilty to an indecent assault and battery charge in Charlestown Municipal Court. Judge Robert McKenna set bail at $100,000 cash. Barthel, who was listed as living at the New England Shelter for Homeless Veterans, is due back in court Aug. 2.

According to State Police, troopers on patrol spotted Barthel and the woman near the Longfellow Bridge. As a trooper approached, Barthel allegedly was seen lying atop the unconscious woman and assaulting her.

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Barthel appeared to be impaired, had slurred speech, and cursed at troopers, according to the report.

“You cops are a [expletive] disgrace,” Barthel allegedly said. “You didn’t see [expletive] and you can’t prove anything. I beat that rape case and my lawyer will beat this [expletive] case, too.’’

The new incident allegedly involving Barthel bears some similarity to another sexual assault case against the defendant that was dropped this year after authorities were unable to locate the victim of the alleged attack.

According to authorities, the woman was rushed to Tufts New England Medical Center for treatment on Oct. 20 after she told police she and Barthel drank alcohol and used heroin together at the Long Wharf Park. Then Barthel demanded that she have sex with him, according to authorities.

When the woman refused Barthel’s demands, he allegedly raped her. The woman did not stay long at the hospital that night, officials said.

Barthel was arrested at the shelter, but authorities could not locate the victim and a rape charge had to be dismissed earlier this year, according to Suffolk District Attorney Daniel F. Conley’s office.

In the new incident, according to State Police, the woman was awakened by Boston Emergency Medical Services personnel, who had responded to the scene around 1 a.m. Sunday. At that point, the 21-year-old woman told State Police, Barthel had repeatedly tried to force her into performing a sex act, and repeatedly ignored her demands that he leave her alone.

“The victim stated that she told Barthel that she had a boyfriend and to leave her alone before she passed out during the encounter,” State Police wrote in the report.

Both State Police and Suffolk District Attorney Daniel F. Conley’s office said the attack allegedly involving Barthel does not appear related to a spate of still-unsolved sexual assaults on the Esplanade, which remain the subject of an intense investigation.

According to State Police, troopers involved in Barthel’s arrest were part of “directed patrols implemented several weeks ago to enhance security for visitors to the Esplanade. ... Among the reasons for the deployment of the patrols are past assaults on the Esplanade.’’