In this article we describe a strategically unusual approach to piperidines via formal [3 + 3] cycloaddition reactions. The scope and limitations of these processes are outlined and their employment in the synthesis of alkaloid natural products is delineated.

[3 + 3] Cycloadditions and related strategies in alkaloid natural product synthesis.

Asymmetric Vinylogous Mannich Reactions: A Versatile Approach to Functionalized Heterocycles

This review of simple indolizidine and quinolizidine alkaloids (i.e., those in which the parent bicyclic systems are in general not embedded in polycyclic arrays) is an update of the previous coverage in Volume 55 of this series (2001). The present survey covers the literature from mid-1999 to the end of 2013; and in addition to aspects of the isolation, characterization, and biological activity of the alkaloids, much emphasis is placed on their total synthesis. A brief introduction to the topic is followed by an overview of relevant alkaloids from fungal and microbial sources, among them slaframine, cyclizidine, Steptomyces metabolites, and the pantocins. The important iminosugar alkaloids lentiginosine, steviamine, swainsonine, castanospermine, and related hydroxyindolizidines are dealt with in the subsequent section. The fourth and fifth sections cover metabolites from terrestrial plants. Pertinent plant alkaloids bearing alkyl, functionalized alkyl or alkenyl substituents include dendroprimine, anibamine, simple alkaloids belonging to the genera Prosopis, Elaeocarpus, Lycopodium, and Poranthera, and bicyclic alkaloids of the lupin family. Plant alkaloids bearing aryl or heteroaryl substituents include ipalbidine and analogs, secophenanthroindolizidine and secophenanthroquinolizidine alkaloids (among them septicine, julandine, and analogs), ficuseptine, lasubines, and other simple quinolizidines of the Lythraceae, the simple furyl-substituted Nuphar alkaloids, and a mixed quinolizidine-quinazoline alkaloid. The penultimate section of the review deals with the sizable group of simple indolizidine and quinolizidine alkaloids isolated from, or detected in, ants, mites, and terrestrial amphibians, and includes an overview of the "dietary hypothesis" for the origin of the amphibian metabolites. The final section surveys relevant alkaloids from marine sources, and includes clathryimines and analogs, stellettamides, the clavepictines and pictamine, and bis(quinolizidine) alkaloids.

Simple indolizidine and quinolizidine alkaloids.

A versatile approach to pyrrolidine azasugars and homoazasugars based on a highly diastereoselective reductive benzyloxymethylation of protected tartarimide

Nucleophilic addition of potassium organotrifluoroborates to chiral cyclic N-acyliminium ions: stereoselective synthesis of functionalized N-heterocycles

A versatile approach to 6-substituted-5-methoxy-δ-lactam framework and application to the formal synthesis of (±)-homopumiliotoxin 223G

Of the various 6-substituted-5-methoxy-δ-lactams 6 were synthesized from α-sulfonyl acetamide 9 in 4 steps in good yield. The key glutarimides 7 were obtained via facile [3+3] annulation. The method featured regioselective introduction of C-6 substituents in glutarimides 7 . Synthesis of tribenzyl lactam 8 and the formal synthesis of (±)-homopumiliotoxin 223G were also reported.

Nein Chen Chang

Papers

A versatile approach to 6-substituted-5-methoxy-δ-lactam framework and application to the formal synthesis of (±)-homopumiliotoxin 223G

A Versatile Approach to 6-Substituted-5-methoxy-δ-lactam Framework and Application to the Formal Synthesis of (.+-.)-Homopumiliotoxin 223G.