A noted Diamond District building has been sold to a Boston-based company, The Post has learned.

TA Realty purchased the 21,492-square foot boutique, 1200 Sixth Ave. for $40 million, sources said.

The building, on the northeast corner of W. 47 St. , also has 22,300 square feet of air rights.

Darcy Stacom’s team at CBRE has been marketing the for the families that have owned it since 1984.

TA is independent but owned by Rockefeller Group International, a subsidiary of Mitsubishi Estate Co. It is TA’s first Big Apple investment. The deal closed April 14.

Since inception in 1982 TA has invested $26.1 billion in real estate in over 945 commercial and multifamily properties for US and foreign investors through both commingled funds and separate core accounts.

The building once housed the Bowery Savings Bank but now has a high producing Pret a Manager and jewelry tenants.

The seven-story boutique building is 70 percent leased, mostly to jewelers. A pre-built program is planned for the few vacant 3,300 square-foot floors. Mitch Konsker and Matt Astrachan of JLL will be handling the leasing, sources said.

The lobby and elevators will be renovated along with an outdoor roof terrace and the retail store fronts.

The additional air rights that create an opportunity to double the size of the building in the future was attractive to the buyers.

Stacom, TA Realty and JLL declined comment.