Asymmetric Synthesis of Taiwaniaquinone H via a Late-Stage Oxidative Decarboxylation.

The asymmetric syntheses of naturally occurring biologically relevant -abietane diterpenoids, (-)-taiwaniaquinone G (), and H () have been reported via a chiral pool strategy starting from commercially available abietic acid. A ring contraction of the middle ring of the [6,6,6]-carbotricyclic abietane diterpenoid core was carried out under the Wolff rearrangement. Finally, the synthesis of (-)-taiwaniaquinone H () was completed via a one-pot CAN-mediated oxidative decarboxylation.

Total Synthesis of (+)-Brevianamides A and B.

(+)-Brevianamides A () and B () are distinguished by their unique bicyclo[2.2.2]diazaoctane structure and have captured the interest of synthetic chemists due to their fascinating array of biological activities.

Biomimetic total synthesis of the reported structure of (+)-selaginedorffone B.

The first enantioselective total synthesis of the reported structure of the structurally unique aromatic tetraterpenoid of anti-cancer potential, (+)-selaginedorffone B (2), has been accomplished from two modified abietane diterpenoids through an intermolecular Diels-Alder reaction between a bio-inspired diene 3 (HOMO counterpart) and dienophile 4 (corresponding LUMO counterpart) in a 23-step sequence, whereas the core framework of the monomeric abietane diterpenoid was constructed alkyne-activated ene-cyclization. Computational analysis was conducted to reveal the intricate regio and diastereoselectivity of this novel Diels-Alder reaction, strengthening the experimental results. The absolute configuration of the synthesized molecule was validated through X-ray studies of late-stage intermediates as well as comprehensive 2D NMR analysis.

Asymmetric Aldol Reactions Catalyzed by Polymeric Self-Assembly with Side-Chain Dipeptide Pendants.

To explore the role of proline amide moieties in polymer-supported organocatalysts, side-chain l-proline-l-alanine (Pro-Ala) dipeptide-containing block copolymers were synthesized, and their catalytic potential for the aldol reaction was explored. The dipeptide monomer (Boc-Pro-Ala-HEMA) was polymerized to prepare block copolymers in the presence of hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) () and hydrophobic poly(methyl methacrylate) () macro-chain transfer agents. Boc group expulsion from the block copolymers produced double hydrophilic () and amphiphilic () polymers.

Total Synthesis of (+)- and (-)-Calycanthine by Means of Thio-Urea-Catalyzed Sequential Michael Reactions of Bis-oxindoles.

A unified catalytic asymmetric approach to naturally occurring piperidinoindoline and pyrrololidinoindoline alkaloids has been realized via the development of a thio-urea-catalyzed sequential Michael addition of bis-oxindole onto nitroethylene (up to 93% ee and >20:1 dr). This strategy offers the total syntheses of either enantiomers of naturally occurring calycanthine.