Following reports that Sotheby’s and Christie’s were competing to handle the collection of the late art collector and Whitney Museum of American Art trustee Emily Fisher Landau at auction this autumn, Sotheby’s announced Wednesday that it will sell the works, estimated to fetch more than $400m.Sotheby’s made the announcement at the Breuer Building in Manhattan, formerly home to the Whitney, which named the fourth floor after Landau in 1994 after she established an exhibition endowment for the institution. In 2010, she pledged nearly 400 pieces valued at almost $75m to the museum. (Sotheby’s announced in June that it would purchase the Breuer Building for its new headquarters in a deal reported to be worth $100m.)Landau, who died last March, began seriously collecting art with money from an insurance payout after 1969, when thieves broke into her home on the Upper East Side and nabbed her jewellery collection, made up of pieces given to her over the years by her husband, Martin Fisher, a real-estate developer. She decided to switch gears and began collecting art. Through her connections to figures like Pace Gallery founder Arne Glimcher and interior designer Bill Katz, Landau built up a world-class collection and formed close relationships with contemporary artists. Around 120 works from her collection are estimated to sell for more than $400m at Sotheby’s New York over two dedicated auctions on 8 and 9 November.The collection at Sotheby’s will be led by Femme à la montre (1932), Pablo Picasso’s portrait of his muse Marie-Thérèse Walter, painted just after his affair with the young woman became public. Landau purchased the painting in 1968, and it hung above the mantel in her New York home for years, according to Sotheby’s specialists. Femme à la montre is estimated to sell in excess of $120m.CSecuring the Last Letter (Boss) (1964) by Ed Ruscha Courtesy Sotheby’sAlso part of the sale will be Securing the Last Letter (Boss) (1964) by Ed Ruscha, whose Los Angeles studio Landau visited multiple times. Based on an earlier work now hanging at the Broad in Los Angeles, Securing the Last Letter (Boss) has been part of major Ruscha exhibitions at both the Whitney and the Hayward Gallery in London.“To the greatest degree, she’s the friend of the artist,” Ruscha said of Landau, according to Sotheby’s. ”Some collectors would prefer not to meet the artist, and I can understand that they don’t want to crack the illusion about somebody whose work they are collecting … She’s different. She’s not afraid to know the artist personally.” Untitled (1958) by Mark Rothko Courtesy Sotheby’sThe sale will also mark the auction debut for Mark Rothko’s untitled 1968 works that relates to the Seagram Murals series, among his most famous. The painting up for sale is stylistically similar to the Seagram paintings and was completed in the same year, according to Sotheby’s specialists. The dark Seagram Murals paintings were originally commissioned for the restaurant inside the Four Seasons in New York’s Seagram Building, but Rothko backed out before telling a reporter he took the job with “malicious intent” and hoped to disgust the high-end restaurant’s patrons. The majority of works from the series are part of museum collections like those of the Kawamura Memorial DIC Museum of Art in Japan, Tate Modern in London and the National Gallery of Art in Washington, DC. A 1986 edition of Jasper Johns’s Flags paintings is expected to sell for between $35m and $45m, and a 1986 camouflage self-portrait by Andy Warhol has a $15m-to-$20m estimate. Willem de Kooning’s Untitled XV (1983) is estimated to sell for between $6m and $8m, while Pink Tulip (1925) by Georgia O’Keeffe could fetch between $3m and $5m. Mark Tansey’s Triumph Over Mastery II (1987) has an $8m-to-$12m estimate.Flags (1986) by Jasper Johns Courtesy Sotheby’sLandau also established the Fisher Landau Center for Art in Long Island City, Queens, and purchased a former parachute-harness factory in the late 1980s to exhibit the collection to the public. It closed in 2017.A nine-figure sale would help Sotheby’s offset a difficult first half of the year for auction houses (Sotheby’s declined to releases its own half-year figures in July).