Amazon’s Long Island City developers, TF Cornerstone, signed a $300 million deal to buy a nearby development site just last week.

The Post has learned the developers, which are the most active in the area, having built hundreds of apartments in the new towers along Center Boulevard, will buy an eight-acre triangular site along the north side of Newtown Creek — a few short blocks south of the Amazon project at 46th Road.

The 326,000 square feet of land at 55-01 Second St. is bounded by 54th Avenue to the north and Vernon Boulevard to the east.

The pricing equates to $187.50 per buildable foot and the developer will have to demolish the current buildings and put in all the infrastructure such as sidewalks and sewers.

It is expected to support four, 400-feet-tall towers with more than 2,000 rental apartments. Under current City rules, about a third of them would be affordable.

Brokers say Amazon’s future influx is already pumping up the demand for apartments, which had stalled, and will now drive up housing prices and rents in the area.

The site has been marketed for over a year by Jimmy Kuhn, Jennifer Schwartzman and David Noonan of Newmark Knight Frank, as The Post first reported.

The Elghanayan family’s TF Cornerstone had previously been selected by the City to develop its land and will now develop the entire new office project for Amazon that will include the adjacent land owned by Plaxall.

The City’s site had been targeted for 1,000 apartments with about a quarter of them affordable while Plaxall’s project was to get just under 5,000 with about 1,250 affordable. Under Amazon’s plan, those units won’t be built.

TF Cornerstone is currently developing 1,200 apartments on Parcel C at Hunter’s Point South, which is the block bordered by Center Boulevard, Borden Avenue, Second Street and 54th Avenue.

While the choice is obvious for the new Second Street land purchase, which is catercorner to its Parcel C, the signing of the sales contract just days before the official Amazon announcement stands out, especially with TF Cornerstone aware there would be big demand coming and fewer apartments in the pipeline.

Both Newmark and TF Cornerstone declined comment through their spokeswomen.