Another major apartment and retail complex is slated for construction in downtown Los Angeles across the street from Mack Urban's proposed residential project in South Park.

Beverly Hills developer Sonny Astani is set to develop the $245-million project on behalf of a new owner, an Arizona investment firm.

Astani, a prolific developer in Los Angeles, secured city approval to build 640 apartments over shops and restaurants on the site bounded by Olive Street, Grand Avenue, Pico Boulevard and 12th Street.

Astani and parking lot giant L&R Group owned the 3-acre parcel now used to park cars and Astani planned to develop the project. But recently they sold the land for $45 million to an investment partnership controlled by Wolff Co., a Scottsdale real estate private equity firm. Astani and L&R bought the property for $29 million in 2012.

As part of the deal, Astani agreed to develop the apartment complex on behalf of the Wolff partnership, which will own it.

The seven-story edifice will be called G12, a reference to its location at Grand and 12th. It will have 1 acre of open space, two swimming pools and two fitness centers. There will be spaces to park 740 bicycles and 595 cars, Astani said.

Work on G12 is set to begin in January and be completed within two years.

Astani is also developing projects elsewhere downtown, in Hollywood and on the Westside.

roger.vincent@latimes.com

Twitter: @rogervincent