Putnam Investments, a retail-focused asset manager with $250 billion under management, is preparing a $1 billion collateralized debt obligation of asset-backed bonds, according to Wall Street professionals. The deal, Putnam's first of the year, will be its third ABS CDO and sixth overall since it first pooled together a collection of junk bonds in 1997. Outsiders note the deal is drawing interest because it is particularly large compared to most multisector structured finance CDOs, which are usually in the range of $300 million because of a limited pool of available collateral. Goldman Sachs is underwriting the deal, according to outsiders. Carl Bell, head of ABS CDO portfolio construction at Putnam in Boston, and Greg Mount, head of CDOs at Goldman in New York, did not return calls.