Complex sentence: In 1957, company researchers isolated the penicillin nucleus 6-aminopenicillanic acid (6-APA); this discovery allowed the synthesis of a number of new semisynthetic penicillins.
Split into simpler sentences: In 1957, company researchers isolated the penicillin nucleus 6-aminopenicillanic acid (6-APA). This discovery allowed the synthesis of a number of new semisynthetic penicillins.