Copper-Catalyzed Arylation of o-Bromoanilides: Highly Flexible Synthesis of Hexahydropyrroloindole Alkaloids

Enantioselective formal total synthesis of dihydrospirotryprostatin B

Spirotryprostatins are representative members of medicinally interesting bioactive molecules of the spirooxindole natural products. In this communication, we present a novel enantioselective total synthesis of the spirooxindole alkaloid dihydrospirotryprostatin B. The synthesis takes advantage of copper-catalyzed tandem reaction of o-iodoanilide chiral sulfinamide derivatives with alkynone to rapidly construct the key quaternary carbon stereocenter of the natural product dihydrospirotryprostatin B.

Enantioselective Total Synthesis of Spirotryprostatin A

In this paper, we disclosed a novel enantioselective total synthesis of spirotryprostatin A (1) in 15 steps with a 7.4% total yield from commercially available 2-iodo-5-methoxyaniline and γ-butyrolactone. The key step features of this synthesis include the copper-catalyzed cascade reaction of o-iodoaniline derivatives with alkynone to introduce the quaternary carbon stereocenter and an aza-Michael tandem reaction to construct the spiro[pyrrolidine-3,3'-oxindole] moiety.

Applications of tert-butanesulfinamide in the synthesis of N-heterocycles via sulfinimines

Chiral sulfinamides are among the best known chiral auxiliaries in the stereoselective synthesis of amines and their derivatives. The most extensively used enantiopure tert-butanesulfinamide emerged as the gold standard among many others over the last two decades. The present review attempts to provide an overview of tert-butanesulfinamide mediated asymmetric N-heterocycle synthesis via sulfinimines and covers literature from 2010-2020. This methodology offers general access to structurally diverse piperidines, pyrrolidines, azetidines, and their fused derivatives that represent the structural motif of many natural products and therapeutically applicable compounds.

Access to 3-Prenylated Oxindoles by α-Regioselective Prenylation: Application to the Synthesis of (±)-Debromoflustramine E

The development of a rapid, highly efficient, and one-pot synthesis of C3-α-prenylated oxindoles with simple reagents is described. The process is based on zinc-mediated α-regioselective prenylation of 3-acylidene-oxindole with commercially available prenyl bromide using inexpensive CeCl₃ as the catalyst. The new transformation tolerates a wide range of 3-acylidene-oxindoles, providing easy access to a variety of functionalized 3-prenylated oxindoles. The synthetic utility of the approach is verified by formal synthesis of the flustramine family alkaloid (±)-debromoflustramine E.

Construction of Spirooxindole Skeleton Through Intramolecular Dieckmann Cyclization

A highly efficient and direct approach was developed to construct the structurally diverse spirooxindole skeleton, which is an important basic motif in natural products. Both the 3,3'-pyrrolidonyl spirooxindoles and spiroindolin-2-one δ-lactones were smoothly obtained by the intramolecular Dieckmann cyclization of oxindoles in excellent yield under mild conditions.

Asymmetric synthesis of δ-amino acid derivatives via diastereoselective vinylogous Mannich reactions between N-tert-butanesulfinyl imines and dioxinone-derived lithium dienolate

A diastereoselective vinylogous Mannich reaction between theN-tert-butanesulfinyl imines and dioxinone-derived lithium dienolate was developed.

Total Synthesis of Dimeric HPI Alkaloids

In this paper, we report a full account of the synthesis of dimeric hexahydropyrroloindole alkaloids and its analogues. The key feature of our new strategy is the novel catalytic copper (10 %) mediated intramolecular arylations of o-haloanilides followed by intermolecular oxidative dimerization of the resulting oxindoles in one pot. This sequential reaction leads to the key intermediates for the synthesis of (+)-chimonanthine, (+)-folicanthine, (-)-calycanthine and (-)-ditryptophenaline. In the presence of catalytic amount of cuprous iodide (10 %), an intramolecular arylation of o-haloanilides followed by an intermolecular oxidative dimerization of the resulting oxindoles leads to a common intermediate for the synthesis of (+)-chimonanthine, (+)-folicanthine and (-)-calycanthine. Based on this cascade sequence, we also developed a flexible strategy towards the asymmetric syntheses of dimeric HPI alkaloids (-)-ditryptophenaline and its analogues.

Total Synthesis of (+)-Chimonanthine, (+)-Folicanthine, and (-)-Calycanthine

Facile, straightforward, and asymmetric total syntheses of (+)-chimonanthine (1), (+)-folicanthine (2), and (-)-calycanthine (3) were accomplished in four to five steps from commercially available tryptamine. The synthesis features copper-mediated asymmetric cyclodimerization of chiral tryptamine derivative, which established a new entry into constructing the sterically hindered vicinal quaternary stereogenic carbon centers of dimeric hexahydropyrroloindole alkaloids in one procedure. An unprecedented base-induced isomerization from the chimonanthine skeleton to the calycanthine skeleton was observed and facilitated the synthesis of (-)-calycanthine (3).

Copper catalyzed sequential arylation−oxidative dimerization of o-haloanilides: synthesis of dimeric HPI alkaloids

A copper catalyzed sequential arylation−oxidative dimerization reaction was developed as the key step for the synthesis of hexahydropyrroloindole alkaloids.

Simple indole alkaloids and those with a nonrearranged monoterpenoid unit

This review summarizes the isolation, structure determination, total syntheses and biological activities of simple indole alkaloids and those with a nonrearranged monoterpenoid unit, with literature coverage from 2012 to 2013.

A General and Practical Palladium-Catalyzed Direct α-Arylation of Amides with Aryl Halides

An efficient system for the direct catalytic intermolecular α-arylation of acetamide derivatives with aryl bromides and chlorides is presented. The palladium catalyst is supported by Kwong's indole-based phosphine ligand and provides monoarylated amides in up to 95% yield. Excellent chemoselectivities (>10:1) in the mono- and diarylation with aryl bromides were achieved by careful selection of bases, solvents, and stoichiometry. Under the coupling conditions, the weakly acidic α-protons of amides (pKa up to 35) were reversibly depotonated by LiO t Bu, NaO t Bu, or NaN(SiMe3)2.