Total Synthesis of (-)-Rhodomollanol A.

An asymmetric approach for the first total synthesis of (-)-rhodomollanol A, a highly oxidized diterpenoid, is described. The efficient synthetic strategy features three key transformations: (1) an oxidative dearomatization-induced (5 + 2) cycloaddition/pinacol-type 1,2-acyl migration cascade to build up the bicyclo[3.2.1]octane skeleton; (2) a retro-Dieckmann fragmentation/vinylogous Dieckmann cyclization cascade to assemble the bicyclo[3.3.0]octane subunit; and (3) a photo-Nazarov cyclization/intramolecular cycloetherification cascade to forge the 7-oxabicyclo[4.2.1]nonane core structure of the natural product.

Total Synthesis of (-)-Pavidolide B: A Ring Contraction Strategy.

A ring contraction approach for the total synthesis of (-)-pavidolide B was developed, which assembles this polycyclic natural product within 13 steps from known chiral alcohol 11. The key features of the strategy include (a) a double Mukaiyama-Michael addition/elimination, (b) a ring-closing metathesis, (c) a Wolff rearrangement, and (d) a late-stage regioselective Schenck ene reaction.

Total Syntheses of (+)-Sarcophytin, (+)-Chatancin, (-)-3-Oxochatancin, and (-)-Pavidolide†B: A Divergent Approach.

A concise and divergent approach for the total syntheses of four cembrane diterpenoids, namely (+)-sarcophytin, (+)-chatancin, (-)-3-oxochatancin, and (-)-pavidolide B, has been developed, and it also led to the structural revision of (-)-isosarcophytin. The key steps of the strategy feature a double Mukaiyama Michael addition/elimination, a Helquist annulation, two substrate-controlled facial-selective hydrations, and a pinacol rearrangement. The described syntheses not only achieved these natural products in an efficient manner, but also provided insight into the biosynthetic relationship between the two different skeletons.

Diastereoselective Total Synthesis of the Euphorbia Diterpenoid Pepluanol†A: A Reductive Annulation Approach.

A new titanium(III)-catalyzed reductive annulation constructed a series of diversely functionalized 1,5-diols in good to excellent yields with respect to a wide scope of vinyl epoxide-aldehyde substrates. Taken together with a Diels-Alder reaction and a substrate-controlled diastereoselective cyclopropanation as additional key steps, the synthetic utility of this novel method has been preliminarily explored by the first and concise total synthesis of the Euphorbia diterpenoid (±)-pepluanol A.