Complex sentence: Robert E. Mnuchin (born 1933) is an American former banker for Goldman Sachs, turned art dealer and gallerist, the founder of the Mnuchin Gallery at 45 East 78th Street, New York.
Split into simpler sentences: Robert E. Mnuchin (born 1933) is a former banker and current art dealer. He is the founder of the Mnuchin Gallery at 45 East 78th Street, New York.