After weeks of speculation that either Christie’s or Sotheby’s would auction off a portion of the storied postwar art collection of the late Ileana and Michael Sonnabend, ARTINFO has learned from sources close to the matter that the family has conducted a private auction through their estate attorney to raise over $500 million to pay off estate taxes.

Antonio Homem, the head of Sonnabend Gallery and the late couple’s adopted son, confirmed the news, but would not identify individual works. “There are two bodies of work that were sold," he said, "that will allow us to pay for the estate taxes.” 

Among the masterpieces sold in two separate transactions, reportedly to billionaire collectors, are Andy Warhols 1963 Silver Disaster # 6 (Double Silver Disaster), in the $35 million range; Roy Lichtensteins Eddie Diptych (1962), in excess of $60 million; and one of Jeff Koonss iconic stainless steel “Rabbits” (1986), for $80 million.

“They shopped it around both auction houses,” said one Manhattan dealer of Sonnabend’s heirs efforts to sell off the collection, “and basically opened an auction on their own through Ralph Lerner,” the noted art-world attorney who represents the family.

Ileana Sonnabend, who was the first wife of late dealer Leo Castelli and was known throughout the art world as the “Mom of Pop Art” and “a cross between Buddha and Machiavelli,” died in New York last October at the age of 92.

She was noted for introducing cutting-edge American artists, including Warhol, Johns, Lichtenstein, and Robert Rauschenberg to Europe through her Galerie Ileana Sonnabend in Paris during the 1960s. After closing shop there, she resettled in New York, opening the Sonnabend Gallery on West Broadway in 1971. That gallery continues to operate today in Chelsea.

She and her late husband, Michael, who died in 2001, had deep holdings in Warhol and other postwar stars; many of these iconic pieces have been on long-term loan at museums including the Princeton University Art Museum and the Newark Museum. Highlights of the extraordinary collection last appeared on public view in 2002–03 in the traveling exhibition “From Pop to Now: Selections from the Sonnabend Collection” at the Frances Young Tang Teaching Museum and Art Gallery at Skidmore College, the Wexner Center for the Arts at Ohio State University in Columbus, and the Milwaukee Art Museum.

Among the Warhol works are Four Campbell Soup Cans, Nine Jackies, a Double Liz, and three different Five Deaths, executed in various colors.

It is understood that a cache of these über-Warhols, as well as the Silver Disaster, were sold to a single collector for a sum in the range of $400 million.

In one deal, the buyer basically got “the core of an extraordinary postwar collection," speculated another top secondary-market dealer who chased the family’s art jewels. "There are clearly a few big new buyers around who are not afraid to spend a billion dollars to quickly buy themselves a great collection.”

It’s still unclear who, apart from attorney Lerner, brokered the transactions.

“I don’t know who in the world is doing the deal,” said one dealer source, “It’s not [William] Acquavella, it’s not [Robert] Mnuchin, and it’s not me.”

Speculation that private dealer Philippe Segalot was involved in brokering the Lichtenstein and Koons transaction could not be confirmed. Segalot declined to comment.

Segalot has been extremely active of late, buying aggressively at auction in London for an anonymous client.

Several dealers who agreed to talk about the apparent mega-sale were dumbfounded at the prices reportedly achieved.

“I just don’t see who’s paying this money,” said the first anonymous dealer quoted above. “It’s not anybody you and I know.”

Before the move to a private auction, it was understood that Christie’s had a leading edge over Sotheby’s in winning the Sonnabend collection.

At Christie’s Post-War and Contemporary art sale last May, Nina Sundell, the daughter and only offspring of Sonnabend and Castelli, sold Johns’s Figure 4 (1959) for a record $17.4 million. It had previously been part of her mother’s collection.