A new approach for the divergent total synthesis of eight ergot alkaloids is reported. The approach allows the first total syntheses of pyroclavine, pibocin A, 9-deacetoxyfumigaclavine C, and fumigaclavine G and also enables the efficient synthesis of festuclavine, costaclavine, epi-costaclavine, and dihydrosetoclavine. The main feature of the synthesis is the use of an unprecedented Pd-catalyzed intramolecular Larock indole annulation/Tsuji-Trost allylation cascade to assemble the tetracyclic core in one step.
We have achieved the first total
synthesis of (−)-principinol
C, which possesses an intriguing and complex 5/7/6/5 tetracyclic skeleton
with eight contiguous stereocenters. The 5/7/6/5 tetracyclic skeleton
of principinol C was assembled using an intramolecular Pauson–Khand
reaction as the key step. This synthetic route represents the first
application of the intramolecular Pauson–Khand reaction of
enyne to construct the 7,5-bicyclic ring system in natural product
synthesis.
A practically useful method for the formation of the highly oxygenated bicyclo[3.2.1]octane ring system through Mn(OAc)3‐mediated radical cyclization of alkynyl ketones was developed, which opens up a new avenue for the total synthesis of a number of highly oxidized diterpenoids. Application of this method enabled the first total synthesis of (−)‐glaucocalyxin A. Other salient features of the synthesis include a highly enantioselective conjugate addition/acylation cascade reaction, a Yamamoto aldol reaction, and an intramolecular Diels–Alder reaction to assemble the A/B ring system.
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