Organic & Biomolecular Chemistry Blog

In a quest for bioactive metabolites from Chinese medicinal plants, Yue-Wei Guo et al. have isolated and characterised a number of novel and exciting natural products from Toona ciliata var. Pubescens, a tall timber tree which can be found widely in south China.

The Toona species have previously led to the isolation of limonoids and protolimonoids. These complex molecules, bearing an elaborate polycyclic skeleton, represent challenging targets for total synthesis and are particularly attractive due to their range of biological activities.

In this paper, the team of collaborative researchers from China and Hungary have isolated nine new limonoids, three of them possessing unprecedented carbon skeletons, along with 5 known analogs. Using advanced NMR techniques, a solid-state TDDFT ECD approach and X-ray analysis, a complete evaluation of their relative and absolute configuration was determined. Biological activities were found for Toonapubesin G (7), showing promising inhibitory activity against the aggressive tumor cell line CDC25B and compound 8a showed significant cell protecting activity against H2O2-induced SH-SY5Y cell damage.

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Protolimonoids and norlimonoids from the stem bark of Toona ciliata var. pubescens
Jian-Rong Wang, Hai-Li Liu, Tibor Kurtán, Attila Mándi, Sándor Antus, Jia Li, Hai-Yan Zhang and Yue-Wei Guo
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C1OB06150J, Paper

Chu-Yi Yu and colleagues present the first stereoselective synthesis of (-)-Erycibelline in this OBC hot article.

(-)-Erycibelline is a naturally occurring dihydroxynortropane alkaloid isolated from the Chinese herb medicine Erycibe elliptilimba, which is used to treat rheumatic disease and is a useful pain-killer.

Yu’s team first synthesized a cyclic nitrone with both nitrone and aldehyde functional groups as the key intermediate by organometallic addition of nitrone followed by oxidation and deprotecton. Subsequent SmI2-induced intramolecular reductive coupling and reductions produced (-)-Erycibelline with good yields.

This neat approach to the nortropane skeleton is versatile and could allow general access to hydroxylated nortropane alkaloids and their analogues, which could be beneficial for treating other diseases.

Download the article now to read more details of this elegant synthesis – it’s free to access for 4 weeks!

A concise stereoselective synthesis of (−)-erycibelline
Z.-L. Zhang, S. Nakagawa, A. Kato, Y.-M. Jia, X.-G. Hu and C.-Y. Yu
Org. Biomol. Chem., 2011, DOI: 10.1039/C1OB06244A

This hot article from John O. Trent et al. at the University of Louisville describes a method for using size exclusion chromatography (SEC) to determine polymorphism in G-quadruplexes.  Current methods for investigating polymorphism rely on modification at either the 3′ or 5′ ends of the sequence, shortening or lengthening putative loop regions to try to produce an enriched configuration to study. But this manipulation of the equilibrium may result in the creation of unnatural species that are not present in vivo.

Trent’s method allows the separation and analysis of quadruplex species without any of the above modifications and has been demonstrated successfully in ten promoter sequences:

Polymorphism and resolution of oncogene promoter quadruplex-forming sequences
M. Clarke Miller, Huy T. Le, William L. Dean, Patrick A. Holt, Jonathan B. Chaires and John O. Trent
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C1OB05891F

While protein assemblies are key to biological processes, their mis-assembly often leads to altered functions such as those found in neurodegenerative diseases. Considerable efforts are ongoing towards the understanding of the assembly processes, either using native or artificial systems.

In this OBC Hot article, Mingming Ma and Dennis Bong at the Ohio State University (Columbus, USA) construct a protein-protein artificial interface and demonstrate that when functionalized with synthetic cyanuric acid and melamine, the streptavidin proteins are able to assemble selectively, based on reversible supramolecular recognition. Such synthetic modules could be used to direct the molecular interactions for the construction of novel biomaterials and functional molecular assemblies.

Interested in proteins, biomaterials or supramolecular chemistry? This OBC Communication is for you!

FREE to access for a period of 4 weeks.

Protein assembly directed by synthetic molecular recognition motifs
Mingming Ma and Dennis Bong
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C1OB05998J, Communication