The Federal Home Loan Bank of Boston said it’s going to court to rescind the purchase of more than 100 mortgage securities for which the bank originally paid nearly $6 billion. FHLB Boston filed a complaint last week in the Department of Business Litigation Session of Suffolk County Superior Court based on the bank’s investments in certain private-label mortgage-backed securities issued by 115 securitization trusts for which the bank paid approximately $5.8 billion. “The Bank is…