Isaac Kassirer’s troubled 10-building East Harlem rental portfolio, now owned by Mack Real Estate Group, faces foreclosure. Freddie Mac and Sabal Capital Partners filed a $47.9 million pre-foreclosure, citing issues with the rent-regulated properties. Kassirer’s Emerald Equity Group previously owned the buildings until early last year when MREG purchased them. The portfolio, mostly rent-stabilized, has struggled due to 2019 rent laws and COVID-19 impacts. MREG, active in multifamily acquisitions, took control of these properties