It is unclear if those highly anticipated, absolute rock-bottom prices on commercial real estate in the U.S. are upon us yet, but for at least one foreign investor, the time is just right to snag a piece of a premier New York City office property. Mazal 485 L.L.C., a joint venture involving Herzliya, Israel-based Optibase Ltd. and Gilmore USA L.L.C., has committed to acquiring 49.5 percent of the 900,000-square-foot office tower at 485 Lexington Avenue in Midtown Manhattan from a subsidiary of SL Green Realty Corp.