There are numerous classes of natural products for which total synthesis is applied to. These include (but are not limited to): terpenes, alkaloids, polyketides and polyethers. Total synthesis targets are sometimes referred to by their organismal origin such as plant, marine, and fungal. The term total synthesis is less frequently but still accurately applied to the synthesis of natural polypeptides and polynucleotides. The peptide hormones oxytocin and vasopressin were isolated and their total syntheses first reported in 1954. It is not uncommon for natural product targets to feature multiple structural components of several natural product classes.