Ethan Penner, founder and vice chairman of Capital America, the commercial real estate lending arm of Nomura Holding America Inc., resigned last week.
Mr. Penner had recently moved to vice chairman from chief executive officer.
In a press release, Capital America said Mr. Penner and the parent company, Nomura, had "different views on how quickly the company should grow and expand into new areas."
Capital America has suffered losses of $200 million, market sources said.
Other sources said Capital America has suffered large losses because it was hedging its commercial mortgage portfolio by writing call options on Treasury securities. When interest rates fell, it lost on the hedge, and its portfolio of commercial mortgages also deteriorated in value, these sources said.
Mr. Penner is a founding father of the market for securities backed by commercial mortgages.