An iron-catalyzed oxidative radical coupling reaction was developed to selectively construct indolofuran or bisphenolic indole cores, which exist in two types of moschamine-related indole alkaloids. Both (+)-decursivine and 4,4″-bis(N-feruloyl)serotonin were biomimetically synthesized by using coupling reactions. The proposed reassignment of the structure of montamine as 4,4″-bis(N-feruloyl)serotonin was excluded.

Alstoscholarisines H–J (1–3), new monoterpenoid indole alkaloids with an unprecedented skeleton created via the formation of a C-3/N-1 bond, were isolated from Alstonia scholaris. Their structures were established by extensive spectroscopic analyses and the assessment of single-crystal X-ray diffraction data. The total synthesis of alstoscholarisine H was achieved via the regioselective nucleophilic addition of pyridinium through a bioinspired iminium ion intermediate followed by Pictet–Spengler-like cyclization.

A Curtius-like rearrangement of hydroxamates to isocyanates was discovered. This reaction was initiated from an iron(II)–nitrenoid complex, which was generated by the iron(II)-catalyzed cleavage of N–O bonds of functionalized hydroxamates. To demonstrate the efficiency of this new Curtius-like rearrangement in synthetic chemistry, a biomimetic strategy for the one-pot preparation of bisindolylmethanes was developed.

A concise total synthesis of (±)-serotobenine via a strategy inspired by the biosynthetic hypothesis for this alkaloid was accomplished. The indolofuran core was constructed by an iron-catalyzed intermolecular oxidative radical cross-coupling reaction developed by our group.

A collective formal synthesis approach to bioactive oxindole alkaloids, including (±)-rhynchophylline, (±)-isorhynchophylline, (±)-mitraphylline, (±)-formosanine, (±)-isomitraphylline, and (±)-isoformosanine, is completed in a protecting-group free manner. Besides multigram-scaled operations, the notable feature of the synthesis is the application of two one-pot, sequential transformations. Namely, two key tetracyclic intermediates pyridinium salt 9 and monoester 14 were prepared by a one-pot N-alkylation/cross-dehydrogenative coupling sequence and a one-pot Michael/Karpocho sequence with minimal purification, respectively.

Hupehenols A–E (3–7) are bioactive octanordammarane triterpenoids, among which hupehenols B (4) and E (7) are the most potent and selective human 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitors (IC50 = 15 and 34 nM, respectively). Herein, the hupehenols were synthesized from protopanaxadiol, the main component of Panax notoginseng. The different synthetic attempts resulted in the stereoselective synthesis of hupehenols A, B, and E for further biological exploration. Notable features of the synthesis included a regioselective epoxide-opening reaction, regioselective acetylation, and a late-stage stereoselective oxa-Michael addition. Semi-synthetic derivatization of these natural products led to the determination of their absolute configurations, a better understanding of their inherent reactivity patterns, and the required C-17 configuration for murine 11β-HSD1 inhibition. These studies provide the basis for the synthesis of 11β-HSD1 inhibitors as potential targets for the treatment of type 2 diabetes.

A copper-mediated cyclization and dimerization of tryptamine or tryptophan was developed to generate a C2-symmetry C3(sp3)–C3(sp3) bridge with two contiguous stereogenic quaternary carbons in one step. Impressively, the ratio between exo and endo cyclization products varies when different protecting groups of Nb are utilized. This dimerization reaction could be conducted in gram scale. With this dimerization method, both endocyclotryptophan (+)-WIN 64821 and exocyclotryptophan (−)-ditryptophenaline were synthesized in 5 steps.

The total synthesis of 4,5-cis unsaturated α-GalCer analogues was achieved, and their immune-response altering activity was assessed in vitro as well as in vivo in mice. Using glycosyl iodide as a glycosyl donor, construction of the sphingosine unit was shortened by four steps and single α-stereoselectivity was achieved in good yield (67%). With regard to the therapeutic use of α-GalCer, the novel analogues (1b and 1c) distinctly induced a Th1-biased cytokine response, avoiding induction of a contradictory response and overstimulation.

The asymmetric synthesis of common aza-tricyclic core of different types of natural alkaloids had been accomplished from commercially available l-Cbz-tyrosine. This practical approach was capable of generating scale-up aza-tricyclic skeleton. Meanwhile, it will facilitate the manipulating functionalities on the aza-tricyclic framework further, for the purpose of target-oriented synthesis of a large number of different natural alkaloids containing this versatile aza-tricyclic structure.

Synthetic endeavors toward (−)-chaetominine via copper-catalyzed radical cyclization are reported. Both of the pyrido[2,3,b]-indole ring (C ring) and imidazolidinone (D ring) are efficiently constructed in one-pot manner. It's unveiled that the newly formed stereo center is controlled by the chiral of alanine, not by tryptophan. With these synthetic discoveries, highly efficient and diastereoselective synthesis of (+)-2,3,14-epi-chaetominine 5 and (−)-11-epi-chaetominine 11 is achieved.

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).

By emitting scent resembling that of organic material suitable for oviposition and/or consumption by flies, sapromyophilous flowers use these flies as pollinators. To date, intensive scent analyses of such flowers have been restricted to Apocynaceae, Annonaceae, and Araceae. Recent studies have suggested that the wide range of volatile organic compounds (VOCs) from sapromyophilous flowers play an important role in attracting saprophagous flies by mimicking different types of decomposing substrates (herbivore and carnivore feces, carrion, and the fruiting bodies of fungi, etc.). In this study, we report the flower visitors and the floral VOCs of Stemona japonica (Blume) Miquel, a species native to China. The flowers do not produce rewards, and pollinators were not observed consuming pollen, thus suggesting a deceptive pollination system. Headspace samples of the floral scent were collected via solid-phase micro-extraction and analysed by gas chromatography coupled with mass spectrometry. Main floral scent compounds were 1-pyrroline (59.2 %), 2-methyl-1-butanol (27.2 %), and 3-methyl-1-butanol (8.8 %), and resulted in a semen-like odor of blooming flowers. The floral constituents of S. japonica were significantly different from those found in previous sapromyophilous plants. An olfaction test indicated that 1-pyrroline is responsible for the semen-like odor in S. japonica flowers. Main flower visitors were shoot flies of the genus Atherigona (Muscidae). Bioassays using a mixture of all identified floral volatiles revealed that the synthetic volatiles can attract Atherigona flies in natural habitats. Our results suggest that the foul-smelling flowers of S. japonica may represent a new type of sapromyophily through scent mimicry.

A facile and straightforward method was developed to construct the fused tetracyclic 3-spirooxindole skeleton, which exists widely in natural products. The formation of the tetracyclic 3-spirooxindole structure was achieved through a transition-metal-free intramolecular cross-dehydrogenative coupling of pyridinium, which were formed in situ by the condensation of 3-(2-bromoethyl)indolin-2-one derivatives with 3-substituted pyridines. As examples of the application of this new methodology, two potentially medicinal natural products, (±)-corynoxine and (±)-corynoxine B, were efficiently synthesized in five scalable steps.

An unprecedented copper-catalyzed intramolecular radical cyclization was developed for the synthesis of 3-hydroxypyrroloindoline skeletons in excellent yields. The 3-hydroxyl group was introduced by trapping the radical intermediate with molecular oxygen or TEMPO. This process represents a unique radical oxidation pathway for tryptamine/tryptophan derivatives and allows a rapid biomimetic synthesis of natural product protubonine A.

Intramolecular hetero-DA reaction and unexpected retro-aldol like ring opening reaction were performed. As a result, six derivatives with different skeletons of vibsane-type diterpenoids were synthesized from vibsanin B within three steps. Moreover, compounds 2, 3, and 6 enhanced the neurite outgrowth of NGF-mediated PC12 cells.Graphical abstract

A small focused library which comprised of l-AA lactone derivatives was built with a facile method. This reported method was optimized by modifying the acidity of the solvent. As a result, 12 l-AA lactones were synthesized. Among these lactones, lactones 8–12 were new compounds. The cytotoxicity of these synthetic compounds were investigated.

New synthetic procedures for the pyrrolo[2,3-b]indole skeleton have been developed via intramolecular annulation of indole derivatives under iodine(III). A series of indole derivatives with different protecting groups or substitutions were explored to facilitate the corresponding pyrrolo[2,3-b]indole compounds in excellent yields.

The glycosphingolipid α-GalCer has been found to influence mammalian immune system significantly through the natural killer T cells. Unfortunately, the pre-clinical and clinical studies revealed several critical disadvantages that prevented the therapeutic application of α-GalCer in treating cancer and other diseases. Recently, the detailed illustration of the CD1d/α-GalCer/NKT TCR complex crystal structural, together with other latest structural and biological understanding on glycolipid ligands and NKT cells, provided a new platform for developing novel glycolipid ligands with optimized therapeutic effects. Here, we designed a series of novel aromatic group substituted α-GalCer analogues. The biological activity of these analogues was characterized and the results showed the unique substitution group manipulated the immune responses of NKT cells. Computer modeling and simulation study indicated the analogues had unique binding mode when forming CD1d/glycolipid/NKT TCR complex, comparing to original α-GalCer.

A concise total synthesis of (±)-serotobenine via a strategy inspired by the biosynthetic hypothesis for this alkaloid was accomplished. The indolofuran core was constructed by an iron-catalyzed intermolecular oxidative radical cross-coupling reaction developed by our group.