A former Goldman Sachs Group Inc director accused of leaking confidential boardroom information has sued US regulators, saying they are trying to unfairly deprive him of a jury trial. Rajat Gupta is fighting civil charges that he tipped one-time hedge fund billionaire Raj Rajaratnam, the central figure in a sprawling insider trading case, about Warren Buffett''s plans to invest in Goldman Sachs at the height of the financial crisis.