The 12-story, 236,000-sf office building stands at 555 Anton Blvd. It was leased for years to Unocal 76 Products before the energy giant was acquired by Tosco Corp., which then moved most of the jobs out of state and left the building vacant.

The current owner, Denver-based Amstar Ltd., bought the complex from Bank of America for about $40 million in 1998. After making roughly $30 million in improvements, the complex was leased to a long list of tenants that include anchor BMC Software, Tickets.com and Epoch Internet.

Though the building is virtually fully leased, the fact that dot-com tenants occupy more than half the space may hurt the property's marketability. "Buyers want real estate here, but a lot of them are worried about the ability of the dot-coms to keep paying their rent," one Orange County broker tells GlobeSt.com. If Wall Street continues to punish technology stocks, the broker says, "a lot more [high-tech] companies are going to have to cut back, and owners could wind up with a lot of empty space."