The enantioselective synthesis of tetracyclic methyllycaconitine analogues

Total Synthesis of Vilmoraconitine

Vilmoraconitine belongs to one of the most complex skeleton types in the C19-diterpenoid alkaloids, which architecturally features an unprecedented heptacyclic core possessing a rigid cyclopropane unit. Here, we report the first total synthesis of vilmoraconitine relying on strategic use of efficient ring-forming reactions. Key steps include an oxidative dearomatization-induced Diels-Alder cycloaddition, a hydrodealkenylative fragmentation/Mannich sequence, and an intramolecular Diels-Alder cycloaddition.

The diterpenoid alkaloids

The diterpenoid alkaloids are a family of extremely important natural products that have long been a research hotspot due to their myriad of intricate structures and diverse biological properties. This chapter systematically summarizes the past 11 years (2009-2019) of studies on the diterpenoid alkaloids, including the "so-called" atypical ones, covering the classification and biogenetic relationships, phytochemistry together with 444 new alkaloids covering 32 novel skeletons and the corrected structures, chemical reactions including conversion toward toxoids, synthetic studies, as well as biological activities. It should be noted that the synthetic studies, especially the total syntheses of various diterpenoid alkaloids, are for the first time reviewed in this treatise. This chapter, in combination with our four previous reviews in volumes 42, 59, 67, and 69, will present to the readers a more completed and updated profile of the diterpenoid alkaloids.

A Method for the Preparation of β-Amino-α,β-unsaturated Carbonyl Compounds: Study of Solvent Effect and Mechanism

An efficient method for the preparation of β-amino-α,β-unsaturated carbonyl compounds is demonstrated. Bench-stable sodium 3-oxo-enolates were prepared from carbonyl compounds, and reacted with amines in the presence of an acid and a desiccant. DFT studies revealed contrasting mechanisms toward the reactivity of aliphatic amines in protic solvents and aromatic amines in aprotic solvents. While the former proceeds through the formation of an imine, the latter passes through the Michael addition-elimination mechanism.

Asymmetric Catalysis Using Chiral Salen-Metal Complexes: Recent Advances

Chiral salen-metal complexes are among the most versatile asymmetric catalysts and have found utility in fields ranging from materials chemistry to organic synthesis. These complexes are capable of inducing chirality in products formed from a wide variety of chemical processes, often with close to perfect stereoinduction. Salen ligands are tunable for steric as well as electronic properties, and their ability to coordinate a large number of metals gives the derived chiral salen-metal complex very broad utility in asymmetric catalysis. This review primarily summarizes developments in chiral salen-metal catalysis over the last two decades with particular emphasis on those applications of importance in asymmetric synthesis.

Total Synthesis of (±)-Quinagolide: A Potent D2 Receptor Agonist for the Treatment of Hyperprolactinemia

A potent dopamine (D2) receptor agonist (±)-quinagolide, which is used for the treatment of hyperprolactinemia, was synthesized using the ring closing metathesis (RCM) approach from meta-hydroxybenzaldehyde as the starting material. The key features of this synthesis are pyrolytic elimination, late-stage expedient synthesis of functionalized trans-fused tetrahydropyridine-3-carboxylates from olefin 6, via conjugate addition-elimination upon acetate 11, followed by RCM and phenyliodine bis(trifluoroacetate) (PIFA)-mediated Hofmann rearrangement of piperidine-3-carboxamide, which enables the synthesis of 3-aminopiperidine skeleton of quinagolide. For the total synthesis of natural products such as ergot alkaloids, late-stage synthesis of functionalized trans-fused tetrahydropyridine-3-carboxylates using RCM and PIFA-mediated Hofmann rearrangement of piperidine-3-carboxamide, which allows quick access to the synthetically challenging 3-aminopiperidine skeleton, are the main achievements of the present work.

Progress towards the synthesis of aconitine: construction of the AE fragment and attempts to access the pentacyclic core

We reported the first successful preparation of fully functionalized aconitine AE fragment and attempts to access the pentacyclic skeleton of aconitine via radical cascade.

Facile one-pot synthesis of a 3-azabicyclo[3.3.1]nonane scaffold by a tandem Mannich reaction

Various 3-azabicyclo[3.3.1]nonane derivatives are readily synthesized directly from aromatic ketones, paraformaldehyde and dimethylamine via a novel one-pot tandem Mannich annulation.

Developing piperine towards TRPV1 and GABAA receptor ligands – synthesis of piperine analogs via Heck-coupling of conjugated dienes

Synthetic analogs of piperine, the pungent alkaloid of black pepper, were identified as selective ligands for either GABA_A or TRPV1 receptors.

The first asymmetric total synthesis of lycoposerramine-R

The first asymmetric total synthesis of lycoposerramine-R was accomplished by a strategy featuring the stereoselective intramolecular aldol cyclization giving a cis-fused 5/6 bicyclic skeleton and a new method for the construction of the pyridone ring via the aza-Wittig reaction, thereby establishing the absolute configuration of the natural product.