Further proposals for polyether antibiotic notation.

The polyether antibiotics reported by the year 1968 were nigericin1) (X-4642)), lasalocid (X-537A2)), X-2062), dianemycin3) and monensin4). Monensin (1) was the only one whose structure was known at that time. In the following decade, the number of distinct polyethers increased from these five to forty-six, almost all of which were structurally assigned. As a result of this rapid growth, a number of different methods of numbering and drawing these compounds have arisen, which sometimes make structural comparisons difficult.