Of ent-calyculin

The calyculins have aroused considerable synthetic interest due not only to their unique polyfunctional structure but also to their intriguing biological activities[ 180]. However, initial synthetic efforts were addressed to (-t-)-calyculin (arbitrarily depicted in the 1986 original paper), which is enantiomeric to the natural occurring compound. The Evans group reported the total synthesis of ent-calyculin A in 1992 [181], which allowed to establish the actual absolute configuration of the natural product. In 1994 Masamune et al. published the total synthesis of the natural enantiomer [182]. Shoiri et al. have also reported a formal total synthesis of calyculin A [183]. Very recently an alternative synthesis of (+)-calyculin A and (-)-calyculin B was reported by Smith [184] whereas the natural calyculin C was obtained by Armstrong and co-workers [185]... 

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