Across the city, real estate executives said deals have been jeopardized by the Bernard Madoff scandal. Residential brokers are taking calls from Madoff investors who have to put their apartments on the market, and developers who had pledged their investments with Madoff as collateral for projects have also been impacted. The investors and developers are now worried that the banks will call in their loans. Finding new lenders will be difficult due to the financial crisis, and because many other real estate investors have been hurt by the Madoff case. “The level of devastation, both financial and on a human level, is astounding,” said Robert Ivanhoe, a lawyer who is representing 10 developers and investors who lost $5 million to $50 million each because of Madoff.