Current Organic Chemistry - Volume 21, Issue 3, 2017

Conjugate addition reactions of organometallic compounds to electron-poor olefins is a versatile synthetic methodology for the formation of new carbon–carbon bonds. However, a careful control of the regioselectivity of the process is needed because of the presence of two electrophilic sites in the activated olefin. This issue is often overcome by employing "soft" nucleophiles such as organocopper and organozinc reagents, because of their high selectivity towards the 1,4-addition. In contrast, organolithium compounds, which are "hard" nucleophiles, generally give access to 1,2-adducts, 1,4-conjugate addition being sometimes observed according to the nature of nucleophiles and/or electrophiles, or to the presence of additives. In this Minireview, we have described some peculiar examples to get an outline of the recent acquisitions in the field of the conjugate additions of functionalized organolithiums to electron-poor olefins. Particular attention is paid to the synthesis of complex structures starting from simple substrates by means of cascade reactions promoted by conjugate addition reactions with organolithiums. Dedicated to the memory of Professor José Barluenga.

Glycosylation of small biologically active molecules, either of natural or synthetic origin, has a profound impact on their solubility, stability, and bioactivity, making glycoconjugates attractive compounds as therapeutic agents or nutraceuticals. A large proportion of secondary metabolites, including flavonoids, occur in plants as glycosides, which adds to the molecular diversity that is much valued in medicinal chemistry studies. The subsequent growing market demand for glycosidic natural products has fueled the development of various chemical and biotechnological methods of glycosides preparation. The review gives an extensive overview of the processes of the synthesis of isoflavones and discusses recently developed major routes towards isoflavone-sugar formation processes. Special attention is given to the derivatives of genistein, the main isoflavone recognized as a useful lead in several therapeutic categories, with particular focus on anticancer drug design. The utility of chemical glycosylations as well as glycoconjugates preparation is discussed in some theoretical as well as practical aspects. Since novel approaches to chemical glycosylations and glycoconjugations are abundant and many of them proved suitable for derivatization of polyphenols a new body of evidence has emerged, indicating that sugar moiety can play a much more significant role, when attached to a pharmacophore, then being a mere “solubilizer”. In many cases, it has been demonstrated that semisynthetic glycoconjugates are much more potent cytostatic and cytotoxic agents than reference isoflavones. Moreover, the newly designed glycosides or glycoside mimics can act through different mechanisms than the parent active molecule.

Organic mechanochromic luminescent materials are under extensive research because of their potential applications in sensors and security. An ideal mechanochromic material should comprise high fluorescent quantum yield in the solid state, significant fluorescent change after mechanical stimulus and high sensitivity to mechanical force, however, few materials reported till now meet all the requisites due to that our limited understanding of mechanochromic mechanism restrains the exploration of high-contrast mechanochromic materials. In order to investigate the mechanochromic mechanism, correlation of mechanochromic luminescence and polymorphic emission is one popular and effective method. During the recent years, great attentions have been paid to cultivate polymorphic crystals with different emissions for mechanochromic molecules. In this review, we s we summarize the polymorphism-dependent and mechanochromic luminescent molecules reported so far, as well as discuss their structure-property relationships, which may provide basic insights for design and synthesis of high-contrast mechanochromic materials. The mechanochromic compounds discussed in this review are categorized into different classes based on their chromophores, including tetraphenylethylene, phenylethylene, BODIPY, polycyclic aromatic hydrocarbon and etc.

The oxime ester moiety exists in a large number of bioactive compounds by a wide range of activities, including antibacterial, antifungal, anti-inflammatory, antioxidant, anti-diabetes and cytotoxic activities. They are also showed interesting insecticidal activities. Furthermore, these compounds are important starting materials in the preparation of photosensitive compositions. Oxime esters are one of the most important and versatile intermediates in organic synthesis. They are very attractive starting materials for the synthesis of various nitrogen and oxygen containing compounds including amine and its derivatives, amides, nitriles, esters, nonaromatic heterocycles, heteroaromatics such as pyrroles, pyridines, quinoline derivatives, miscellaneous, imines, N-heterocycles, etc. This valuable review article summarizes efforts to use oxime esters as reagent and catalysts in the synthetic chemistry. We have classified the applications of these compounds in the organic synthesis based on the desired products. The focus will be on synthesis of heteroaromatic compounds from titled compounds. This interesting review article presents the synthetic applications of oxime esters.

Recently, the development of nanotechnology and nanomaterial has promoted extremely the application of drug delivery systems in the biomedical field. However, the drug delivery into the central nervous system (CNS) is limited because the existence of the blood brain barrier (BBB). Therefore, to develop the efficient drug delivery systems (DDS) for crossing the BBB into the lesions is necessary. The holistic DDS, which successfully transfer drug into the brain, should be explored on the basis of biodegradable and non-cytotoxic nanomaterial. In this review, we discussed the applications of nanoparticles-mediated DDS in the CNS and focused on the varied nanocarrier strategies used for crossing the BBB and targeting the brain lesions, such as poly (PEG, PLA, and PLGA) covalent-attached to nanoparticles strategies, lipid nanocarrier DDS strategy, polymeric/dendritic nanocarrier DDS strategies, magnetic nanocarrier DDS strategy, and other (carbon nanotubes, viral, gold, silica etc.) nanocarrier DDS strategies. In conclusion, the platform carrying nanoparticles-based drug vehicle is vital and promising for developing the special brain drug delivery system. In future multifunctional nanocarriers may play more important role in treating various neurological diseases.