SHANGHAI – When it went public in April 2007, Simcere Pharmaceutical Group quickly became the largest Chinese pharmaceutical listed in the U.S. Despite a good early performance, the stock never lived up to its promise. The firm’s share price crashed to below $5 after the global financial crisis and has been lingering at below $10 since late 2011 . Simcere, originally a maker of generics that has expanded into biologicals, will go private before the end of the year.