Current Organic Chemistry - Volume 21, Issue 6, 2017

In recent decade, gold nanoclusters with atomic precision (AunLm where L = ligand) have been demonstrated as a new and promising class of nanocatalysts. The AunLm catalysts of different sizes possess unique crystal and electronic structures, thereby providing an excellent opportunity to correlate the intrinsic catalytic performance with the catalysts’ structure as well as to study mechanisms of chemical reactions catalyzed over gold nanoparticles. In this review, controlled synthesis of atomically precise gold nanoclusters and their thermal stabilities are explained. We demonstrate important roles played by the gold nanoclusters for catalytic reactions, including selective oxidation and hydrogenation as well as carbon-carbon coupling reactions. Tailoring of the catalysts’ functions is discussed in terms of size-specificity, ligand engineering (e.g., aromatic vs aliphatic), and doping effects (e.g., copper, silver, palladium, and platinum). The proposed reactions’ mechanisms and the structureactivity relationships at the atomic detail are presented.

Much attention has been paid to coenzyme Q10 (CoQ10) as a treatment for cardiovascular and neurological diseases because of the antioxidant activity since 1959. CoQ10 is non-toxic. It has a wide range of health effects and is a popular commercial supplement. Despite these advantages, CoQ10 faces synthetic challenges and low yield. The synthesis of CoQ10 is very difficult. Researchers have described several semi-synthetic strategies. This review offers a detailed discussion of recent advances in the semi-synthesis of CoQ10. Four strategies are presented including side chain direct introduction, side chain extension, carbon addition and Diels-Alder rearrangement. Most semi-synthetic strategies employ side chain extension to synthesize CoQ10 because it increases the stereoselectivity and coupling efficiency of the side chain configuration. Side chain extension greatly improves the utilization of solanesol and reduces cost. This article presents the latest details in CoQ10 synthesis.

Achmatowicz reaction has emerged as an efficient tool in organic synthesis since its discovery in 1971 by Achmatowicz Jr.The original protocol went through several advantageous variations. Biocatalytic and metal catalyzed versions of this reaction are some of the significant achievements, which further enhanced its effectiveness. The pyranone product of the Achmatowicz reaction is a versatile building block for the synthesis of bioactive scaffolds, drugs and natural products. The present review covers the application of the Achmatowicz reaction in the synthesis of natural products and bioactive molecules reported from 1971 to date. It has been divided into seven sections on the basis of the core structures of the natural products synthesized utilizing the Achmatowicz reaction. We believe that this comprehensive review will attract many more organic chemists to explore its utility in organic synthesis, especially in the synthesis of bioactive natural products as well as drugs in their efficient and atom economical synthesis.

Spermidine alkaloids are polyaminated macrocycles containing a lactam ring, which are biosynthetically derived from L-Orn or L-Arg via putrescine intermediates. The presence of these polyamines in nature is very limited, occurring in only a few plant families, and therefore the isolation of spermidine alkaloids serves chemotaxonomic purposes. The interest in the isolation and synthesis of these alkaloids also results from the structural complexity and broad range of bioactivity attributed to these macrocyclic structures. In recent years, several research groups have been dedicated to these triaminated compounds and previously unknown natural products, or already described structures in new plant species, with potential biological applications have been reported. Novel synthetic strategies and the application of more recent synthetic methodologies have allowed new perspectives for the development of new bioactive molecules. The latest progress on the isolation, identification, biological activity, and chemical synthesis of spermidine alkaloids is summarized in this review.

Background: Recent studies highlighted that biochar efficiency to improve soil fertility is enhanced after it is blended with fresh organic materials. It was suggested that organic coating of inner-porous biochar surfaces acts as a kind of “glue” for plant-nutrients, thereby allowing their slow release towards plant-roots and/or microorganisms. Objective: The aim of the present study is to improve the understanding of the nature of the interactions between fresh organic matter and a poplar biochar. Method: Two fluorinated organic models were used as target molecules in order to apply heteronuclear (i.e. 19F) fast field cycling (FFC) NMR relaxometry. Results: The results suggest that organic coating can be stabilized by charge transfer interactions (involving electron- rich systems of fresh organic matter and electron-poor sites provided by biochar), water bridging (between biochar surface and fluorinated compounds) and van der Waals interactions (occurring between the biochar aromatic system and the carbon chain of the fluorinated compound). Conclusions: The weak interactions outlined above may be responsible for an induced dipole on the biochar organic- cover. The induced dipole, in turn, can be involved in the adsorption of plant nutrients (which adsorb only marginally on the un-coated biochar), while maintaining their availability for plants.