Answer:
Percy Julian's most significant achievement was his work on the synthesis of cortisone and other medicinal compounds from plant sterols. At the time, cortisone was a newly discovered drug that had significant potential to treat a variety of diseases, including arthritis and other inflammatory conditions. However, the only source of cortisone was from the adrenal glands of animals, which made the drug expensive and difficult to produce in large quantities.
Julian's work involved developing a method to synthesize cortisone from soybeans, a process that had never been achieved before. This was a major breakthrough that not only made cortisone more widely available but also paved the way for the synthesis of other important medicinal compounds. Julian's work on steroid synthesis also had important implications for the development of the birth control pill and other hormone-based therapies.
Overall, Percy Julian's achievement in synthesizing cortisone and other medicinal compounds from plant sterols was a major breakthrough in the field of pharmaceuticals and had a significant impact on the treatment of many diseases.