DAMASCUS/LONDON/DUBAI (Reuters) -As his enemies closed in on Damascus, Bashar al-Assad, who ruled over Syria with an iron fist for 24 years, used a private jet to spirit away cash, valuables and confidential documents mapping the corporate web behind his wealth. Yasar Ibrahim, the president's top economic adviser, arranged the leasing of the plane to transport Assad's treasured assets, relatives, aides and presidential palace personnel to the United Arab Emirates aboard four flights, according to an account of the operation pieced together by Reuters from more than a dozen sources. Ibrahim, who ran the economic and financial office of the presidency, was instrumental in creating a network of entities Assad used to control swathes of Syria's economy, often acting as a front for the former ruler, according to U.S. sanctions notices, as well as experts on Syria's economy and one source inside Assad's business network.