Advances and Strategies towards Synthesis of Aspidosperma Indole Alkaloids Goniomitine.

Goniomitine is of the aspidosperma alkaloid family, with an angularly fused tetracyclic skeleton housing an all-carbon quaternary carbon chiral center alongside an aminal functional group. This natural product has garnered attention as a synthetic target due to its intriguing molecular architecture and anti-proliferative activity in recent years. Following the first synthesis of (-)-goniomitine by Takano in 1991, synthetic chemists have developed various methods. This review provides an overview of the methodologies used in the synthesis of goniomitine in racemic and enantiopure forms via divergent construction indole framework, indole functionalization, and the integrated oxidation/reduction/cyclization (iORC) sequence from 1991 to 2023.

Progress towards the Total Syntheses of Amaryllidaceae Alkaloids γ-Lycorane.

γ-Lycorane, a degradation product of the Aromaticaceae alkaloid lycorine, is one of the most attractive molecules in the Aromaticaceae family. It remains a popular target for synthesis due to its pentacyclic structure, which presents a vehicle for demonstrating the utility of new synthetic strategies. Various synthetic methods have been developed by synthetic chemists since the first synthesis of γ-lycorane by Nasuo in 1966. Thus, this review presents an overview of the literature on the ways utilized within the synthesis of γ-lycorane in racemic and enantiopure forms via electrophilic arylation, Pd-catalyzed C-C coupling, Bischler-Napieralski cyclization, Pictet-Spengler cyclization, photocyclization, radical cyclization, chiral pool synthesis, chiral auxiliary-mediated synthesis, and catalytic asymmetric synthesis, ranging from 1966 to 2022.

Chiral Tertiary Amine Catalyzed Asymmetric [4 + 2] Cyclization of 3-Aroylcoumarines with 2,3-Butadienoate.

Coumarins and 2H-pyran derivatives are among the most commonly found structural units in natural products. Therefore, the introduction of 2H-pyran moiety into the coumarin structural unit, i.e., dihydrocoumarin-fused dihydropyranones, is a potentially successful route for the identification of novel bioactive structures, and the synthesis of these structures has attracted continuing research interest. Herein, a chiral tertiary amine catalyzed [4 + 2] cyclization of 3-aroylcoumarines with benzyl 2,3-butadienoate was reported. In the presence of Kumar's 6'-(4-biphenyl)-ß-iso-cinchonine, the desired dihydrocoumarin-fused dihydropyranone products could be obtained in up to 97% yield and 90% ee values.

Enantioselective Construction of Chiral Cyclopropa[c]coumarins via Lewis Base-Catalyzed Cyclopropanation.

The first highly enantioselective construction of chiral cyclopropa[c]coumarins was described. Using commercially available (bis)cinchona alkaloid (DHQ)2PYR as the chiral Lewis base catalyst, together with Cs2CO3 as the achiral base, the reaction of a series of coumarin-3-carboxylate and 3-benzoyl coumarins with tert-butyl 2-bromoacetate could give rise to the corresponding cyclopropa[c]coumarins bearing three continuous chiral stereocenters in 83-93% ee and 90-97% ee, respectively. The reaction is proposed to proceed via an in situ generated ammonium ylide intermediate.

A catalyst-free, one-pot three-component aminomethylation of α-substituted nitroacetates: theoretical and experimental studies into the rate-accelerating effects of the solvent methanol.

3, 2, 1 go! An unprecedented one-pot, catalyst-free, three-component aminomethylation of α-substituted nitroacetates, formalin, and amines has been reported, thereby enabling the highly efficient synthesis of α,ß-diamino acid precursors with great structural diversity.

Direct amination of α-substituted nitroacetates using di-tert-butyl azodicarboxylate catalyzed by Hatakeyama's catalyst ß-ICD.

We report the first example of catalytic asymmetric direct amination of α-monosubstituted nitroacetates using di-tert-butyl azodicarboxylate. The simple and easily available Hatakeyama's catalyst ß-ICD 11 was found to be a highly enantioselective catalyst for this reaction.

A Hg(ClO4)2·3H2O catalyzed Sakurai-Hosomi allylation of isatins and isatin ketoimines using allyltrimethylsilane.

It is reported that Hg(ClO(4))(2)·3H(2)O could efficiently activate the cheap but less reactive allyltrimethylsilane for the allylation of isatins or isatin ketoimines, with catalyst loading down to 0.1 mol %. This is the first example of Sakurai-Hosomi allylation of ketoimines using allyltrimethylsilane. A rare example of chiral mercury catalysis is also reported.

A facile method for the synthesis of oxindole based quaternary alpha-aminonitriles via the Strecker reaction.

The direct alpha-cyanoamination of isatins using TMSCN has been developed, which is carried out in methanol without any catalyst. A new bifunctional cinchona alkaloid-based phosphinamide catalyst 7 could promote the Strecker reaction of isatins derived ketimine with TMSCN in up to 74% ee.