The stereochemistry of spiropiperidine cyclizations (histrionicotoxin, part I)

A Formal Synthesis of (-)-Perhydrohistrionicotoxin Using a Cross Metathesis-Hydrogenation Approach

The development of an efficient, high yielding six-step convergent synthesis of the semisynthetic alkaloid (-)-perhydrohistrionicotoxin is described. The key transformations include the cross metathesis of a Brønsted-acid masked primary homoallylic amine with a vinyl cyclohexenone and a regioselective palladium catalyzed hydrogenation. This sequence generated the advanced Winterfeldt spirocyclic precursor in 47% overall yield, with a longest linear sequence of five steps.

Synthetic approaches towards alkaloids bearing α-tertiary amines

Alkaloids account for some of the most beautiful and biologically active natural products. Although they are usually classified along biosynthetic criteria, they can also be categorized according to certain structural motifs. Amongst these, the α-tertiary amine (ATA), i.e. a tetrasubstituted carbon atom surrounded by three carbons and one nitrogen, is particularly interesting. A limited number of methods have been described to access this functional group and fewer still are commonly used in synthesis. Herein, we review some approaches to asymmetrically access ATAs and provide an overview of alkaloid total syntheses where those have been employed.

Thirty-five years of synthetic studies directed towards the histrionicotoxin family of alkaloids

This article brings together for the first time reviews of all the synthetic attempts towards the spirocyclic histrionicotoxin alkaloids published since the discovery of the group in 1971. This covers 5 total syntheses of the fully unsaturated parent alkaloid HTX-283A, 7 total syntheses of perhydrohistrionicotoxin, 15 total syntheses of other members of this alkaloid family, 25 formal syntheses, and 19 partial syntheses involving the successful formation of the core azaspirocyclic structure but lacking advancement towards the target structure.