text: 21st century By late 2000, Dai-Ichi's broker Jones Lang LaSalle had placed the entirety of the office building, which had become known as the Citigroup Center, for sale. Dai-Ichi and Citigroup—the latter of which had been formed in 1998 through a merger of Citicorp and the Travelers Companies—arranged to jointly sell both condominium shares. Richard and Eric D. Hadar, a father-and-son venture, bid $725 million for Dai-Ichi's ownership stake in January 2001. For the purchase, Eric Hadar had arranged a $525 million first mortgage from Deutsche Bank and a $150 million mezzanine loan from the government of Singapore. The sale was delayed after Boston Properties offered to buy Dai-Ichi's stake. Eric Hadar's company, Allied Partners, along with Boston Properties, ultimately finalized their purchase of both condominium shares that April. The price was $755 million, including closing costs and taxes, and Citigroup relocated to 399 Park Avenue. One of the stilts was structurally reinforced following the September 11 attacks, and protective bollards were installed on the sidewalk.
  Boston Properties bought Allied Partners' stake in the Citigroup Center in 2006 for $100 million. The same year, Boston Properties began rebranding the building as 601 Lexington Avenue. A new Lexington Avenue lobby was constructed and the tower stories' entrance was relocated from 53rd Street to Lexington Avenue. In addition, a ramp was installed on 53rd Street and a reception area was added to the northern entrance of St. Peter's Church. The name change took effect in 2010. Boston Properties was also considering selling naming rights to the building. By 2013, Citigroup only occupied three stories at the Citigroup Center. The next year, Boston Properties sold a 45 percent ownership stake in the Citigroup Center, along with proportional stakes in the Atlantic Wharf Office Building and 100 Federal Street in Boston, to companies associated with Norges Bank Investment Management. These firms paid a combined $1.5 billion.