Rhazinilam-leuconolam family of natural products: a half century of total synthesis

Synthesis of All Ring Sizes of Medium-Sized Heterocycles Bridged Biaryls via VQM-Enabled Diversity-Oriented Synthetic Strategy

Herein, for the first time, the controllable, accurate, and diverse synthesis of all ring sizes of medium-sized (8- to 11-membered) indole-derived bridged biaryls has been realized by using ingeniously designed o-alkynylnaphthols that feature cyclic amines with adjustable ring sizes. The transformation may proceed through a DBN-mediated in-situ generation of vinylidene ortho-quinone methides/indole-ring formation/ring expansion cascade sequence, which is characterized by acceptable to excellent yields and good functional group tolerance.

Enantiospecific Synthesis of Tetrahydroindolizines from Spiro-cyclopropanecarboxylated Sugars

A facile two-step enantiospecific synthesis of 5,6,7,8-tetrahydroindolizine scaffolds has been developed via TMSOTf-promoted [3 + 2] cycloaddition between carbohydrate-derived spirocyclic donor-acceptor cyclopropanecarboxlates and alkyl/aryl nitriles followed by an intramolecular Mitsunobu reaction of the resulting chiral 2/5-(4-hydroxybutyl)pyrrole derivatives.

Medium-Sized Ring Expansion Strategies: Enhancing Small-Molecule Library Development

The construction of a small molecule library that includes compounds with medium-sized rings is increasingly essential in drug discovery. These compounds are essential for identifying novel therapeutic agents capable of targeting "undruggable" targets through high-throughput and high-content screening, given their structural complexity and diversity. However, synthesizing medium-sized rings presents notable challenges, particularly with direct cyclization methods, due to issues such as transannular strain and reduced degrees of freedom. This review presents an overview of current strategies in synthesizing medium-sized rings, emphasizing innovative approaches like ring-expansion reactions. It highlights the challenges of synthesis and the potential of these compounds to diversify the chemical space for drug discovery, underscoring the importance of medium-sized rings in developing new bioactive compounds.

Enantioselective Total Synthesis of (-)-Hunterine A Enabled by a Desymmetrization/Rearrangement Strategy

The first enantioselective total synthesis of (-)-hunterine A is disclosed. Our strategy employs a catalytic asymmetric desymmetrization of a symmetrical diketone and subsequent Beckmann rearrangement to construct a 5,6-α-aminoketone. A convergent 1,2-addition joins a vinyl dianion nucleophile and the enantioenriched ketone. The endgame of the synthesis features an aza-Cope/Mannich reaction and azide-olefin dipolar cycloaddition to complete the pentacyclic ring system. The synthesis is completed through a regioselective aziridine ring opening.

Structural diversity, hypothetical biosynthesis, chemical synthesis, and biological activity of Ganoderma meroterpenoids

Covering: 2018 to 2022Meroterpenoids found in fungal species of the genus Ganoderma and known as Ganoderma meroterpenoids (GMs) are substances composed of a 1,2,4-trisubstituted benzene and a polyunsaturated side chain. These substances have attracted the attention of chemists and pharmacologists due to their diverse structures and significant bioactivity. In this review, we present the structures and possible biosynthesis of representative GMs newly found from 2018 to 2022, as well as chemical synthesis and biological activity of some interesting GMs. We propose for the first time a plausible biosynthetic pathway for GMs, which will certainly motivate further research on the biosynthetic pathway in Ganoderma species, as well as on chemical synthesis of GMs as important bioactive compounds for the purpose of drug development.

Catalytic asymmetric synthesis of medium-sized bridged biaryls

Despite the persistent presence of medium-sized (seven- to nine-membered) scaffolds in natural products and biologically active molecules, their asymmetric syntheses have always been considered a formidable task; therefore, they have remained underdeveloped when compared to the enantioselective synthesis of five- and six-membered ring scaffolds. One important class of such medium-sized ring frameworks includes seven- to nine-membered biaryl bridged carbo- and heterocycles. These medium-ring-sized biaryl frameworks possess more configurational stability than the related smaller ring structures and are common features of valuable natural products, bioactive compounds, chiral catalysts, and molecular motors. Due to these exciting properties and broad applications, over the last few years, the catalytic enantioselective synthesis of medium-sized bridged biaryls has seen an upsurge. This highlight article describes the development of organocatalysed and transition-metal catalysed transformations for procuring seven-, eight-, and nine-membered bridged biaryls bearing a chiral axis/one or more asymmetric carbon centres.

A Modular Synthesis of the Rhazinilam Family of Alkaloids and Analogs Thereof

A short, modular strategy for synthesizing three representative alkaloids of the (±)-rhazinilam family and 10 non-natural analogs is described. The protocol involves a radical addition/cyclization cascade reaction that assembles the tetrahydroindolizine system decorated with appropriate groups for a subsequent Pd-mediated cyclization, which generates the nine-membered lactam.