2.2.2. PMA

Petromyric acids A and B (PMA and PMB) are dehydroxylated tetrahydrofuranyl fatty acids that were isolated from larval washing extracts from the sea lamprey *Petromyzon marinus* in 2018 [26]. From the washing extract, four fatty acids related to the acetogenin family were identified: (+)-PMA (**(+)-17**), (−)-PMA (**(***−***)-17**), (+)-PMB (**(+)-18**), and (−)- PMB (**(***−***)-18**) (Figure 5). Their chemical structure was elucidated by NMR spectroscopy and confirmed by chemical synthesis and X-ray crystallography.

**Figure 5.** Structure of (+)-PMA (**(+)-17**), (−)-PMA (**(***−***)-17**), (+)-PMB (**(+)-18**), and (−)-PMB (**(***−***)-18**).

Sea lampreys are anadromous fishes that migrate, using their olfactory cues to orientate, from the ocean to freshwater to find a suitable spawning stream. When approaching river mouths, the decision of which stream is optimal to spawn in is taken using their olfactory system to detect a pheromone emitted from larval sea lampreys. When investigating larval washing extracts, four fatty acids were identified, but only **(+)-17** has proven to be the

pheromone that guides lamprey adults. However, its enantiomer, **(***−***)-17**, does not produce the same behavioral effect. Fatty acid analogues have been reported to be pheromones in insects, but this is the first identification in fish. The sea lamprey is a destructive invader in the Laurentian Great Lakes, while in Europe, its population has decreased precipitously, so **(+)-17** can be used for the control and conservation of their populations.

Although they have a high potential for application, to the best of our knowledge, no total synthesis has been reported so far for these compounds.
