A former downtown office building recently converted to a luxury residential rental by a venture of Vanbarton Group and Metro Loft Management is being sold to the latter for $450 million.

Longtime downtown developer Nathan Berman of Metro Loft Management has signed an agreement to buy 180 Water St. from his majority conversion partners, Richard Coles and Gary Tischler of the Vanbarton Group, sources confirmed. The pricing comes to $785,340 per unit.

Adam Doneger and Joshua King led the Cushman & Wakefield team representing Vanbarton in the sales process.

Their “180 degree” conversion turned the 1960s office building into a 573-unit amenity-filled rental designed by Avinash K. Malhotra with interiors and market-rate apartments designed by CetraRuddy. Three of the four retail spaces totaling 11,819 square feet are still available through Winick Realty Group.

The building is wrapped by Pearl, John and Water streets. When its lease was running out with the City’s Human Resources Administration, the building was sold by Melohn Properties in July 2013 for $151 million to Vanbarton.

Berman, the undisputed king of downtown office-to-rental conversions, was brought in as the developer with less than a 10 percent stake in 2014, he told the Commercial Observer.

Vanbarton was previously the lender on Berman’s conversion of 116 John and had also sold Berman the former stock exchange building at 20 Broad, which is being converted into 530 apartments.

When HRA moved out in 2015, the nearly $100 million transformation of 180 Water began. The partners carved out a large atrium in the center and added a roof top amenity structure with a fitness center, yoga studio, entertaining kitchen and dining room, gaming area, and landscaped roof deck with an outdoor pool.

Rents for the handful of remaining units range from $2,690 for a studio to $7,190 for a three-bedroom. All have 10-foot ceilings, large windows, stripped wood flooring and kitchens with custom paneled appliances and marble counters.

Vanbarton also owns 160 Water and this project may provide a model for a future redevelopment of that office building.

Last year Berman sold his 63/67 Wall St. conversion to Rockpoint for $421.5 million, or $521,666 per apartment.

By comparison, Harry Macklowe paid $585 million to the Bank of New York Mellon for vacant 1 Wall, which is being converted mostly into condos and retail.

In 2012, Forest City Ratner sold the new 8 Spruce St. to TIAA-CREF for $512 million while Vornado paid Westbrook $496,320,000 for the older mixed-use Independence Plaza on the west side of downtown.

Cushman & Wakefield declined to comment, while neither Vanbarton nor Metro Loft returned calls.