A Manhattan man died of an apparent overdose after an ambulance failed to show up at his building for more than an hour, forcing frustrated cops to finally rush him to the hospital, to no avail, police and law-enforcement sources said.

Adam Benhammou, 22, of East Harlem was showing signs of an overdose at his building on East 116th Street near Lexington Avenue at 5:13 p.m. Saturday when a 911 call was made asking for first responders’ help, according to authorities and sources.

Adam Benhammou, 22, suffered an apparennt drug overdose in this East Harlem building Saturday.…