US hotel group Starwood Capital is to sell four key French properties, including the famed Martinez in Cannes and the Concorde Lafayette in Paris, to a Qatari investor, a union official said yesterday. Starwood Capital’s Groupe du Louvre will hold a meeting on Thursday with the sale of the Martinez, Concorde Lafayette, Hotel du Louvre and the Palais de la Mediterranee in Nice on the agenda, union representative Claude Levy told AFP. “A promise to sell has been signed recently and there will be an announcement on the matter on June 28,” said Levy.  A source close to the sale said the buyer was Katara Hospitality, formerly known as Qatar National Hotels Company.