The bankruptcy estate of Lehman Brothers acquired another stake in apartment developer Archstone and blocked a potential purchase by Equity Residential (EQR). Lehman's estate already owned 47% of Archstone, and the Friday purchase ups its holdings to 73.5%. Equity Residential, founded by Sam Zell, readied its own $1.33 billion bid for half of the Archstone stake held by Bank of America (BAC) and Barclays PLC (BCS). That triggered a right of first offer clause for Lehman, which filed for Chapter 11 protection in 2008. The Lehman deal closed Friday, according to a Securities and Exchange Commission filing Monday and first reported by The Wall Street Journal. The bankruptcy estate first showed interest in a bid in December. The rest of the Archstone stake owned by Bank of America and Barclays remains up for grabs for Equity Residential for 30 days. Lehman can match that offer as well. Archstone held ownership in 428 developments domestically and in Europe as of Sept. 30. Chicago-based Equity Residential has investments in more than 400 communities in the United States, according to the company. Write to Andrew Scoggin. Follow him on Twitter @ascoggin.