NEW YORK (Bloomberg) Pulsar Re Ltd, a Bermuda-based reinsurance company, filed a lawsuit accusing Lehman Brothers Holdings Inc of looting $450 million in cash that was supposed to be held in a segregated account.Lehman took the cash in a “one-sided repurchase transaction” intended to help salvage the investment bank’s failing business, Pulsar alleged in the complaint filed yesterday in US Bankruptcy Court in Manhattan.Pulsar said it assumed $1 billion of risk from Lehman’s Bermuda-based reinsurance unit, Lehman Re Ltd. To collateraliSe its obligations and cover the risk, Pulsar said it transferred $450 million in cash that was supposed to be held by Lehman Re in a segregated custodial account at Lehman’s brokerage unit.Without telling Pulsar, the cash was transferred to Lehman Commercial Paper Inc. in a repurchase transaction “backed by illiquid and materially overvalued assets,” Pulsar claimed. Lehman Re was later liquidated, and Pulsar lost its money, according to the complaint.Pulsar is suing the Lehman holding company and Lehman Commercial Paper by asking a bankruptcy judge to declare the existence of a constructive trust, so it can obtain the misappropriated cash. Pulsar said it learned that its cash was improperly transferred only after Lehman filed for bankruptcy in September 2008.Kimberly Macleod, a Lehman spokeswoman, didn’t immediately return an e-mail seeking comment.Kirkland & Ellis LLP is representing Pulsar in the lawsuit.Once the fourth-largest investment bank, New York-based Lehman filed the biggest bankruptcy in US history, listing $613 billion in debts.