WHITE PLAINS, N.Y.

The long dispute over the estate of socialite philanthropist Brooke Astor ended Wednesday with a settlement that frees $100 million for charities and cuts by more than half the amount going to the son convicted of bilking her.

The agreement among Astor’s descendants and the New York institutions she loved ended a five-year legal fight that the judge feared would consume the entire estate.

Westchester County Surrogate Judge Anthony Scarpino signed the agreement Wednesday afternoon. State Attorney General Eric Schneiderman announced the details.

Astor died in 2007 at the age of 105.

Schneiderman said the settlement benefits several institutions, principally the Metropolitan Museum of Art, the New York Public Library and New York City’s public schools.

He said it cuts by more than half — to $14.5 million — the amount going to Astor’s son, Anthony Marshall.

Marshall and the charities had disagreed on which of several wills and revisions expressed Astor’s true intent. In the midst of the estate battle, in 2009, he was convicted in Manhattan of taking advantage of his mother’s dementia, partly by engineering changes to her will. He has appealed.

That case shocked New York, where Astor was a popular woman-about-town well into her 90s.

Other charities benefiting from the settlement include Central Park and Prospect Park in New York, the Bronx Zoo, Historic Hudson Valley, Carnegie Hall, New York University, Rockefeller University, the Pierpont Morgan Library, the city’s Animal Medical Center and Trinity Episcopal Church.

The attorney general’s office stepped into the case to protect the charities, and Schneiderman said he was happy that the agreement “honors Mrs. Astor’s final wishes and benefits New York’s landmark educational and cultural institutions.”

Anthony Marx, president of the Public Library, said the settlement means Astor’s legacy “can continue as she intended.” Thomas Campbell, director and CEO of the Met, also said Astor’s intentions had been honored.

Waddell Stillman, president of Historic Hudson Valley, called the settlement “amazing” and said it “avoids costly litigation that would have depleted Mrs. Astor’s estate.”

Scarpino said in 2007, at a court session involving 15 lawyers, that he feared the attorneys “will be happy to litigate this matter to the very end of this stream of money that’s there.”

That brought comparisons to Dickens’ novel “Bleak House,” in which a large inheritance led to a case that persisted for generations. By the time it was settled, almost nothing was left for the descendants.

In the Astor case, three descendants who were minors when the case began have turned 18 in the meanwhile. Anthony Marshall’s son, Philip, who opposed his father in court, is another beneficiary. Philip Marshall is a professor at Roger Williams University in Rhode Island.

Anthony Marshall’s lawyer, Ken Warner, said he was pleased that the settlement had been reached.

“He is almost 88 years old, and much prefers closure to an expensive and protracted litigation over his mother’s estate,” Warner said.

The settlement does not detail the current size of the estate, but in 2007 it was estimated at $198 million. It also does not specify how much each party is receiving, but Schneiderman said it establishes a $30 million Brooke Astor Fund for New York City education.

Under the 2002 will that forms the basis for the settlement, the Met and the Public Library were to get 25 percent each of the amount going to charity.

The Metropolitan Museum of Art released a statement saying they were “deeply gratified” the charitable intentions of the late Astor have been honored.

“Under this settlement, the Museum will receive approximately $20 million from the estate, which will be used to support the institution’s curatorial programs and art acquisitions, as Mrs. Astor wished,” the statement said.

Codicils that would have given millions more to Anthony Marshall at the expense of Astor’s charities were ignored. Marshall’s share is reduced by $12.3 million, which he must repay the estate because of his criminal conviction.

Astor donated millions to the arts and the poor after the 1959 death of her husband, Vincent Astor, heir to a fortune generated in real estate and the fur trade by his great-great-grandfather, John Jacob Astor.

While Brooke Astor’s estate was substantial, it was dwarfed by some others. Leona Helmsley, the real estate queen who died the same year, left more than $4 billion to charity.

Astor’s estate may soon be worth a little more, however. Some of her designer jewelry, furniture and decorative arts are being auctioned in September at Sotheby’s. Her Westchester estate was recently sold for $6.4 million.