Anshu Jain, the former Deutsche Bank AG co-chief executive officer, is joining Cantor Fitzgerald LP as president, restarting his career at a much smaller firm after leaving Germany’s largest bank amid mounting legal and regulatory problems. Jain, 53, will help the closely held company expand in areas including fixed-income and equities trading as well as prime brokerage, Cantor Chairman and CEO Howard W. Lutnick said Monday in a phone interview. The firm is looking to capitalize as stiff regulations force global investment banks, including many in Europe, to pare businesses and pull back from some clients.