Organic & Biomolecular Chemistry Blog

While L-sugars are promising candidates in medicinal chemistry, such as L-ribose-containing nucleosides, only their D-forms naturally occur, thus prompting the need for an efficient synthetic methodology.

In this aim, Gaik-Khuan Chuah et al. at the National University of Singapore have devised a novel route to access rare L-lyxose and L-ribose in a simple 5-step procedure, leading to significantly increased yields and greener conditions as compared to previous reports.

To overcome the critical step for the oxidation of D-sugar to the corresponding D-lactone, the authors have used a heterogeneous catalyst – palladium-bismuth supported on carbon – and molecular oxygen, thus eliminating the need for bromine often used for this oxidation. The catalyst can easily be separated from the reaction mixture and reused, which enhances even further the relevance of this novel protocol.

Interested? Why not read this Hot Article now, it will be free to access for the next 4 weeks upon a simple registration process.

Reference
A heterogeneous Pd–Bi/C catalyst in the synthesis of L-lyxose and L-ribose from naturally occurring D-sugars
Ao Fan, Stephan Jaenicke and Gaik-Khuan Chuah
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C1OB06116J, Paper

In this Hot article, Adam T. Slósarczyk and Lars Baltzer from Uppsala University, Sweden, report on the conjugation of designed polypeptides to a small organic molecule as a strategy for the recognition and binding of phosphorylated proteins.

Conjugating a polypeptide to the zinc chelating ligand led to a dramatic increase in affinity and selectivity towards phosphoproteins, here caseins, however this concept for binder development is thought to be widely applicable and ‘high-affinity binders can conveniently be developed for a variety of proteins including those with posttranslational modifications for which small molecule recognition elements are available.’, report the authors.

Curious to learn more? Read the full article now, FREE to access for the next 4 weeks.

Reference
The molecular recognition of phosphorylated proteins by designed polypeptides conjugated to a small molecule that binds phosphate
Adam T. Ślósarczyk and Lars Baltzer
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C1OB06154B, Paper

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.

This article will be FREE to access for the next 4 weeks:

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