Allopumiliotoxin

The compounds of the pumiliotoxin-A class are primarily found in the skins of frogs, toads, and other amphibians and are used as a chemical defense mechanism to ward off predators, microorganisms, and ectoparasites.

Among allopumiliotoxins, those with a β-oriented C-7 hydroxyl group have shown greater activity in comparison to α-epimers of this position.

Once the compound’s specific class is determined, it’s given a number based on its molecular weight.

These biologically active compounds are complex and have structural variations that allow for specific molecular recognition.

Compounds that rotate a plane of polarized light clockwise are referred to as dextrorotatory and are preceded by a (+) sign.

Compounds that rotate a plane of polarized light counterclockwise are referred to as levorotatory and are preceded by a (−) sign.

The main problem with allopumiliotoxin synthesis arises from the alkylidene side chain because the stereochemistry of it can be difficult to control by Wittig-type functionalizations.

[6] Total synthesis of (+)-allopumiliotoxin 267A was achieved using a chiral dihydropyridone intermediate that was formed from the addition of ethyl lithiopropiolate to the N-acylpyridinium salt which results from the reaction of (+)-trans-2-(α-cumyl)cyclohexyl chloroformate and 4-methoxy-3-methyl-5(triisopropylsilyl)pyridine.

[10] (+)-Allopumiliotoxin 339A has been synthesized using an iodide-promoted iminium ion alkyne cyclization followed by condensation with acetylenic salt.