A partnership of Newport Beach-based Koll Real Estate Group and NorthStar Capital Partners of New York has purchased and plans to renovate a vacant four-story, 50,000-square-foot building in Century City. The group bought the 32-year-old office building at 1940 Century Park East from a private investment group, 1940 Associates, for $6 million. It will spend an additional $6.5 million to gut the building to its steel frame and rebuild it for an entertainment-related tenant or tenants. Construction is expected to start in two weeks for July completion. Koll officials say they decided to renovate the building because of its location in the tight Century City market, where only two other office spaces of that size are available. The purchase is Koll's first in Los Angeles. The company recently opened an office in Beverly Hills to target other acquisitions. North Star Capital Partners is a real estate investment group formed last month by former executives of Apollo Real Estate Advisors and Goldman, Sachs & Co.