Michelle Tan has been let go from Credit Suisse First Boston where she was a v.p. collateralized debt obligation structurer, according to a person at the firm familiar with the situation. She reported to Chris Ricciardi, managing director and head of structured credit products. Tan could not be reached for comment and Ricciardi did not return calls. It could not be determined whether her slot would be filled. Ricciardi's group originates and structures all CDO deals that are not backed by high-yield bonds, which includes investment-grade, structured finance or alternative CDOs.