A nephew of famed late Manhattan interior designer David Barrett lost a $45,000 painting to his brother in a coin toss — and now he’s flipping out.

Richard Barrett, whose uncle hobnobbed with heiresses Doris Duke and Barbara Hutton and created lavish window displays for Bergdorf Goodman and Saks Fifth Avenue, inherited half of David’s $5.6 million fortune after the designer died at age 85 in 2008.

Richard’s younger brother, Alan, inherited the other half.

But after Richard, 50, lost a coin toss with Alan, 49, for ”Jug with Lemon” by Colombian artist Fernando Botero that was part of the estate, he filed a lawsuit to get back the pricey painting, holding up payouts to the estate’s two executors and his sibling in the meantime.

At one point, Richard called his brother to complain about the general distribution plan concocted by the two co-executors, leaving a hate-filled message on his sibling’s answering machine, according to the surrogate-court documents.

Richard vowed to send his three adversaries “to the gallows” and “bury [them] under f–king concrete,” the papers say.

A lawyer for the estate joked in the documents that the Florida-based brothers held the coin toss because King Solomon wasn’t available to settle the dispute.

But one of the executors, Steven Sonet, was more somber in recounting the drama in the lawsuit.

“I . . . kept [Richard] apprised of estate matters as long as he spoke to me without epithets,” Sonet said in an affidavit.

Richard told The Post that he is not looking out for just his own interests.

“This case is about more than my share of my uncle’s estate,” Richard said in a statement released by his lawyer. “It is about my uncle, his legacy, his reputation and his family.

“I want the world to know what my uncle worked for, collected and accomplished in his storied career, and how he inspired others.”

Barrett’s collection also included Botero’s painting “Still Life (with Mandolin).”