Current Organic Chemistry - Volume 22, Issue 20, 2018

Rapid developments in protein engineering, immunology and pharmaceutical research have led to immense demands for synthetic polypeptides. Several polypeptides synthesizing strategies are now available, among which solid-phase synthesis and solution- phase synthesis are especially relevant. This review pretended to compare these two synthesizing strategies with no bias, appreciate their advantages, drawbacks and limitations, and forecast their developmental trends. It also introduced several other special synthetic strategies, and their applications were presented in detail.

Background: Heterocyclic compounds have received much attention due to their versatile applications in the field of medicinal chemistry as well as organic chemistry. Objective: The main objective of this review is to give an overview of the recent application of β-cyclodextrin catalyzed one–pot multicomponent reactions for the synthesis of different assemblies of heterocycles. Method: In this review, we have summarized the one-pot multicomponent approach towards the synthesis of heterocyclic compounds by using β-cyclodextrin as a supramolecular catalyst. It is outlined under the headings (1) five-membered heterocyclic compounds and (2) six and seven membered heterocyclic compounds. Conclusion: This review outlined the recent key developments in the synthesis of different O-, N- and S- containing heterocyclic scaffolds, following MCRs published by using β-CD and its derivatives as a supramolecular catalyst for the synthesis of five, six and seven membered heterocycles. The versatility of cyclodextrins and modified cyclodextrins will encourage chemists to develop new heterocyclic molecules by using multicomponent reactions in the near future.

In several cases, the occurrence of methylation on oxygen site of an organic molecule is not a straightforward process. Most of the O-methylations take place with hydroxyl groups of carboxylic acids, phenols, and alcohols, affording methyl esters, aryl methyl ethers, and alkyl methyl ethers, respectively. Polysaccharides are polyhydric alcohols that have received special interest for methylation purpose. A number of methylating agents have been employed to affix methyl group to molecule matrix via oxygen atom, and are, to cite but a few, methanol, methyl iodide, diazomethane, dimethyl sulfate, dimethyl carbonate, methyl triflate, tetramethylammonium salts and trimethyl phosphate. To the variety of existing OH-substrates and methylating agents, the myriad of organic and inorganic substances that play key roles in catalyzing the methylation reactions are added. The odd-even effect of acidic/basic character of a catalyst promotes the selectivity of methylation, hence the desired product. In most cases, every couple of catalyst/methylating agent brings about the O-methylation of the substrate through a unique mechanism.

Atorvastatin is an aromatic compound that acts selectively in the liver as an inhibitor of HMG-CoA reductase and cholesterol synthesis. The iodination of aromatic compounds has been widely applied for the preparation of potential pharmaceuticals and bioactive molecules. Herein, an iodinated atorvastatin was synthesized using chloramine- T (CAT) intermediate via an electrophilic substitution reaction. The obtained product was elucidated via elemental analysis, mass spectrometry and 1H-NMR techniques. A comparison of experimental 1H-NMR chemical shifts of the iodinated atorvastatin with the corresponding predicted ones obtained with GIAO method at the B3LYP/LanL2DZ confirmed the desired structure. Furthermore, the favourable electrophilic substitution site was confirmed by the Fukui indices calculations of the heavy atoms of the parent atorvastatin at DFT with the same level of theory.

An efficient and ligandless catalytic system was developed for the Suzuki- Miyaura coupling reactions of potassium aryltrifluoroborates in pure water. Using TEAB as additives, Pd(OAc)2 was found to be very efficient for the Suzuki-Miyaura coupling of potassium aryltrifluoroborates with various aryl and heteroaryl bromides in pure water with Na2CO3 as a base, affording the desired products in moderate to excellent yields.