Anthopleura elegantissima pheromone

Not all releaser pheromones are sex attractants. One alternative example of a releaser pheromone is the sending out of an alarm message, warning other members of the species that some threat is at hand. The California sea anemone Anthopleura elegantissima provides a neat example of alarm signaling. 

Anthopleura elegantissima is a small, common sea anemone. It is a bit less than 1 inch across normally. However, it can do some interesting chemistry. If one is wounded, it emits an alarm pheromone as a warning to neighboring members of the same species. When this alarm pheromone hits its receptor, the recipient anemone reacts with a series of quick flexes of its basal tentacles, followed by withdrawing the tentacles into the mouth that then snaps shut. This takes a bit less than 3 seconds overall. 

The colonial sea anemone Anthopleura elegantissima responds with characteristic contraction to a pheromone released by wounded conspecifics. This alarm response is highly characteristic, includes rapid bending and shortening of the tentacles and depression of the oral disk. In 1975, by extensive ion exchange column chromatography, (3-carboxy-2,3-dihydroxy-A(A(Af-trimethyl)-l-propanaminium chloride (50) was isolated as a pure crystalline substance.116 It showed alarm pheromone activity with a median concentration of 0.35 nmol 1 1 and was named anthopleurine. Comparison of spectral data between natural and synthetic compounds revealed that anthopleurine had a structure of 4-amino-4-deoxy-L-threonic acid betaine hydrochloride.117... 

The partial hydrolysis of 4a with methanolic potassium hydroxide followed by selective carboxylic acid reduction with excess borane and treatment of the resulting monoalcohol with methanesulfonyl chloride affords methyl 4-0-methanesulfonyl-2,3-0-isopropylidene-L-threonate (43). Facile displacement of the mesylate with azide followed by ester hydrolysis and catalytic reduction to an amine provides 4-amino-4-deoxy-2,3-0-isopropylidene-L-threonic acid (44). Mild acidic deprotection and ion-exchange desalting of 44 yields (2i ,3 S)-4-amino-4-deoxy-L-threonic acid (45), which has been utilized for the preparation of anthopleurine 46, the alarm pheromone of the sea anemone Anthopleura elegantissima [4] (Scheme 11). 

Dimethyl tartrate 6.260) is also an important chiral template. The first step was protection of the diol moiety to give acetonide 6.261. A multi-step transformation followed which gave 4-amino-2,3-dihydroxybutanoic acid, 6.262. This dihy-droxyamino acid was converted to anthopleurine (4-amino-2,3-dihydroxybutanoic acid, or 4-[N,N,N-trimethylammonium]-2,3-dihydroxybutanoic acid, 6.263), an alarm pheromone of the sea anemone Anthopleura elegantissima. ... 

A. elegantissima is a preferred prey of the aeolid nudibranch Aeolidiapapillosa. Interestingly, anthopleurine (50) remains in the tissue of nudibranch, and leakage of the pheromone causes the alarm response in other anemone individuals for several days.118,119 Consequently, the predator may help in transmission of the alarm pheromone, which can reduce the severity of predation on Anthopleura. 

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