The Calyciphylline B-type Alkaloids: Total Syntheses of (–)-Daphlongamine H and (–)-Isodaphlongamine H

The first total synthesis of the complex hexacylic Daphniphyllum alkaloid (–)-daphlongamine H in enantioenriched form has been accomplished. Key to the success of the strategy are a complexity-building Mannich reaction, efficient cyclizations, and a highly diastereoselective hydrogenation to assemble multigram quantities of the tricyclic core bearing four contiguous stereocenters. Following construction of the hydro-indene substructure by means of a Pauson–Khand reaction, endgame redox manipulations delivered the natural product. Importantly, the synthetic studies have also given access to (–)-isodaphlongamine H and led to a revision of the reported structure of deoxyisocalyciphylline B, which resulted in the proposal of a modified biosynthetic pathway to the calyciphylline B-type alkaloids.

The Calyciphylline B-type Alkaloids: Total Syntheses of (–)-Daphlongamine H and (–)-Isodaphlongamine H

The first total synthesis of the complex hexacylic Daphniphyllum alkaloid (–)-daphlongamine H in enantioenriched form has been accomplished. Key to the success of the strategy are a complexity-building Mannich reaction, efficient cyclizations, and a highly diastereoselective hydrogenation to assemble multigram quantities of the tricyclic core bearing four contiguous stereocenters. Following construction of the hydro-indene substructure by means of a Pauson–Khand reaction, endgame redox manipulations delivered the natural product. Importantly, the synthetic studies have also given access to (–)-isodaphlongamine H and led to a revision of the reported structure of deoxyisocalyciphylline B, which resulted in the proposal of a modified biosynthetic pathway to the calyciphylline B-type alkaloids.

Stereoselective Synthesis of Tetrahydrofuran Lignans

This short review aims to summarize the reports on stereoselective synthesis of naturally occurring tetrahydrofuran lignans published during the period of 2006 to 2018. The stereoselective construction of non-natural tetrahydrofuran frameworks is not included in this review.1 Introduction2 Stereoselective Synthesis of 2,5-Diaryltetrahydrofuran (CL5-a)2.1 Synthesis of CL5-a via Friedel–Crafts Arylation or Nucleophilic Addition/Reduction of γ-Butyrolactones2.2 Synthesis of CL5-a via Intramolecular Cyclization of 1,4-Diaryl­butanediols2.3 Synthesis of CL5-a via Diastereoselective Hydrogenation of Furan Derivatives2.4 Synthesis of CL5-a via Cycloaddition Reaction of Substituted Cyclopropane­ Derivatives3 Stereoselective Synthesis of 2-Aryl-4-benzyltetrahydrofuran (CL5-b)4 Stereoselective Synthesis of 3,4-Dibenzyltetrahydrofuran (CL5-c)5 Conclusions