Sotheby's auction of $180m Van Gogh challenged over claims it was 'sold under duress'

Auction house Sotheby's says it is working to resolve a dispute over the intended sale of a painting by Vincent van Gogh.Châtaigniers en Fleurs, which carries an estimate of $180m (£136m), is due to go under the hammer in New York on Wednesday.But representatives acting for heirs of the Fischer family - earlier German owners of the work - say it may have been sold under duress during the rise of the Nazis.Sotheby's say its own "extensive research" has not established this, but say they will work with the family to try and reach a solution."Sotheby's takes provenance and restitution matters extremely seriously and has undertaken extensive research into the ownership history of Châtaigniers en fleurs," Sotheby's told the BBC in a statement."We are aware of the concerns recently raised by representatives of the Fischer heirs and have been in dialogue with them regarding the painting's history."While our research to date has not established that the painting was sold under duress, we recognize the importance of engaging thoughtfully and constructively with the family and are committed to working toward a mutually satisfactory resolution."The painting - whose name translates as Blossoming Chestnut Trees - is being sold as part of a set called the Blaquier-Arrieta Collection.Sotheby's website details the provenance of the oil painting and how it has researched the artwork changing hands since 1890.It says Samuel Fischer - a famous German publisher - acquired it 1909 before it was passed down in his family after his death in 1934.The painting was deposited with Paul Cassirer in Amsterdam in 1932 or 1933 before it went to Henriette and Marcel Kapferer in Paris in 1936, Sotherby's says.Four other owners have had it since before it was put up for auction this year.Fischer family heirs have instructed a lawyer who, according to the New York Times, external, has written to Sotherby's.He is said to have told the auction house the painting was sold in Amsterdam before World War Two because of financial losses the Fischer family's publishing company suffered under the Nazis.The BBC has contacted the lawyer for comment.