After an attempt to lower the troubled mortgage on a host of prime Upper Manhattan apartments and retail spaces fell through, the valuable note is now being marketed and should sell close to its face value of $70 million, The Post has learned.

The portfolio’s owners include high-profile investors Neil Rubler and Richard Mack, who have been negotiating to resolve the situation, sources said.

But the special servicer has just hired David Schechtman of Eastern Consolidated to sell what has now, with interest, become an $80 million defaulted first mortgage on 446 residential units in eight large, well-maintained buildings (which also have retail spaces) along Broadway, Riverside Drive and Fort Washington Avenue in Washington Heights and Morningside Heights.

About 75 percent of the units in this so-called Broadway Portfolio II have regulated rents. Addresses include 3885, 3900, 3915 and 4455 Broadway and stretch from roughly 160th Street to 190th Street; 66-72, 80 and 86 Fort Washington Ave.; and 884 Riverside Drive.

The Post has found some of the buildings are on the city’s current lien list due to small repairs and other items dating back to 2008, but all the major tax bills seem to have been paid.

Schechtman, Mack and Rubler did not return calls for comment.