Willem de Kooning’s Untitled XXI will come up as a highlight at Christie’s 20th century evening sale in New York in May. Estimated in in excess of $20 million the painting is fresh to the market and has been in the same private collection for more than 30 years. It was painted in de Kooning’s studio in East Hampton in 1977, a year when he turned out a group of radiant, large-scale abstractions that had a new level of mastery about them. Art historians regard 1977 as a highpoint of his career, his annus mirabilis, or “miraculous year,” as the British critic David Sylvester wrote. The art market has confirmed that view: three of de Kooning’s top four highest prices achieved at auction were for paintings from 1977.