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The daphnezomine A‐type subfamily of Daphniphyllum alkaloids structurally features a unique aza‐adamantane core skeleton and anticipates efficient strategies for completing their syntheses to thoroughly investigate their biological activities. Herein, divergent total syntheses of (−)‐daphnezomines A and B and (+)‐dapholdhamine B have been accomplished in 16–20 steps from a known epoxide via rapid construction of a common core intermediate. The present work features a Ti‐mediated radical cyclization to establish the azabicyclo[3.3.1]nonane ring system, an intramolecular Heck reaction to install the bridgehead all‐carbon quaternary stereocenter, a tandem deprotection/reduction/keto amine‐carbinolamine tautomerization to furnish the aza‐adamantane backbone, and an NIS‐promoted 6‐endo‐trig aminocyclization to assemble the (+)‐dapholdhamine B backbone. [ABSTRACT FROM AUTHOR]

(+)‐Mannolide C is a complex hexacyclic C20 cephalotane‐type diterpenoid featuring a highly strained 7/6/6/5 tetracyclic core containing eight consecutive stereocenters and two bridging lactones. The first asymmetric total synthesis of (+)‐mannolide C has been accomplished by lipase‐mediated resolution, Ru‐complex‐catalyzed double ring‐closing metathesis (RCM) reactions, NiII‐catalyzed diastereoselective Michael addition, and MnIII‐catalyzed allylic oxidation as the key transformations. [ABSTRACT FROM AUTHOR]

Cyclopianes are novel diterpenes featuring a highly strained 6/5/5/5 tetracyclic core embedded with 6–8 consecutive stereocenters. The concise total syntheses of (−)‐conidiogenone B, (−)‐conidiogenone, and (−)‐conidiogenol have been accomplished in 14–17 steps. The present work features a HAT‐mediated alkene–nitrile cyclization to access the cis‐biquinane, a Nicholas/Pauson–Khand reaction to construct the linear triquinane, and a Danheiser annulation to afford the congested angular triquinane skeleton. [ABSTRACT FROM AUTHOR]

A general and efficient protocol was developed for the synthesis of polysubstituted pyridines from propargyl amines and unsaturated carbonyl compounds through a tandem condensation/alkyne isomerization/6π 3‐azatriene electrocyclization sequence. This process was found to be applicable to a wide range of readily available substrates (30 examples, up to 95 % yield) and could be readily performed on a preparative (20 g) scale. By taking advantage of this method for late‐stage pyridine incorporation, we successfully completed the collective total synthesis of suveoline, norsuveoline, and macrophylline. 6π to py: A wide range of polysubstituted pyridines were synthesized in a straightforward manner from propargyl amines and unsaturated aldehydes through a tandem condensation/alkyne isomerization/6π 3‐azatriene electrocyclization sequence in good yields. This transformation was used as a key step in the collective total synthesis of suveoline, norsuveoline, and macrophylline (see scheme). [ABSTRACT FROM AUTHOR]

Described herein is the first asymmetric total synthesis of (+)-harringtonolide, a natural diterpenoid with an unusual tropone imbedded in a cagelike framework. The key transformations include an intramolecular Diels-Alder reaction and a rhodium-complex-catalyzed intramolecular [3+2] cycloaddition to install the tetracyclic core as well as a highly efficient tropone formation. [ABSTRACT FROM AUTHOR]

An efficient synthesis of an oxo-bridged 7/6-bicyclic precursor that is potentially useful for the construction of harringtonolide has been realized through a [4+3] cycloaddition reaction. Meanwhile, an unexpected rearrangement reaction, which could be used for the fast assembly of spirocycles, was found during the double elimination attempts. [ABSTRACT FROM AUTHOR]

The first enantioselective total synthesis of (−)-salprzelactone, a seco-norabietane diterpenoid has been accomplished in only three steps. Key transformations of the synthesis include an intermolecular aldol reaction and lactonization. [ABSTRACT FROM AUTHOR]