Antheridic acid total synthesis

Retrosynthetic analysis of antheridic acid produced a totally different plan of synthesis from that which had been employed for the structurally related target gibberellic acid. The synthesis of antheridic acid, which included a number of novel steps, allowed definitive assignment of structure and revised stereochemistry at C(3). 

The enantioseiective total synthesis of antheridic acid involves the key O-heterocyclic intermediate 375 produced by an intramolecular addition... 

The enantioselective total synthesis of (+)-antheridic acid was accomplished by E.J. Corey and co-workers using the Lewis-acid-mediated vinyicyciopropane-cyciopentene rearrangement as the key step. This key transformation was not possible under thermal conditions however, the use of excess diethylaluminum chloride in DCM gave rise to the rearranged product in excellent yield. 

Corey, E. J., Kigoshi, H. A route for the enantioselective total synthesis of antheridic acid, the antheridium-inducing factor from Anemia phyllitidis. Tetrahedron Lett. 1991, 32, 5025-5028. 

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