Complex sentence: One of the most notable Armenians who resided in Portugal was Calouste Gulbenkian, a wealthy Armenian businessman and philantropist, who made Lisbon his headquarters for his businesses.
Split into simpler sentences: One of the most notable Armenians who resided in Portugal was Calouste Gulbenkian. He was a wealthy Armenian businessman and philantropist, who made Lisbon the headquarters for his businesses.