Supporters of the Detroit Institute of Arts reacted with dismay Thursday to Sotheby’s announcement that it will auction A. Alfred Taubman’s legendary art collection, as that means it will not go to the museum.

Sotheby’s statement said the 500-plus works “valued in excess of $500 million” will be on the block in four auctions starting Nov. 4 in New York. The news release called it “the most valuable private collection ever offered at auction.”