An enamine is an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine. Enamines are versatile intermediates.
Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric products in unequal amounts."
The Robinson annulation is a chemical reaction used in organic chemistry for ring formation. It was discovered by Robert Robinson in 1935 as a method to create a six membered ring by forming three new carbon–carbon bonds. The method uses a ketone and a methyl vinyl ketone to form an α,β-unsaturated ketone in a cyclohexane ring by a Michael addition followed by an aldol condensation. This procedure is one of the key methods to form fused ring systems.
The docking theory of olfaction proposes that the smell of an odorant molecule is due to a range of weak non-covalent interactions between the odorant [a ligand] and one or more G protein-coupled odorant receptors. These include intermolecular forces, such as dipole-dipole and Van der Waals interactions, as well as hydrogen bonding. More specific proposed interactions include metal-ion, ion-ion, cation-pi and pi-stacking. Interactions can be influenced by the hydrophobic effect. Conformational changes can also have a significant impact on interactions with receptors, as ligands have been shown to interact with ligands without being in their conformation of lowest energy.
The vibration theory of smell proposes that a molecule's smell character is due to its vibrational frequency in the infrared range. This controversial theory is an alternative to the more widely accepted docking theory of olfaction, which proposes that a molecule's smell character is due to a range of weak non-covalent interactions between its protein odorant receptor, such as electrostatic and Van der Waals interactions as well as H-bonding, dipole attraction, pi-stacking, metal ion, Cation–pi interaction, and hydrophobic effects, in addition to the molecule's conformation.
Civetone is a macrocyclic ketone and the main odorous constituent of civet oil. It is a pheromone sourced from the African civet. It has a strong musky odor that becomes pleasant at extreme dilutions. Civetone is closely related to muscone, the principal odoriferous compound found in musk; the structure of both compounds was elucidated by Leopold Ružička. Today, civetone can be synthesized from precursor chemicals found in palm oil.
Macrocycles are often described as molecules and ions containing a ring of twelve or more atoms. Classical examples include the crown ethers, calixarenes, porphyrins, and cyclodextrins. Macrocycles describe a large, mature area of chemistry.
The article concerns the total synthesis of galanthamine, a drug used for the treatment of mild to moderate Alzheimer's disease.
In organic chemistry, the Paal–Knorr synthesis is a reaction used to synthesize substituted furans, pyrroles, or thiophenes from 1,4-diketones. It is a synthetically valuable method for obtaining substituted furans and pyrroles, which are common structural components of many natural products. It was initially reported independently by German chemists Carl Paal and Ludwig Knorr in 1884 as a method for the preparation of furans, and has been adapted for pyrroles and thiophenes. Although the Paal–Knorr synthesis has seen widespread use, the mechanism wasn't fully understood until it was elucidated by V. Amarnath et al. in the 1990s.
In organic chemistry, aldol reactions are acid- or base-catalyzed reactions of aldehydes or ketones.
The Hajos–Parrish–Eder–Sauer–Wiechert reaction in organic chemistry is a proline catalysed asymmetric aldol reaction. The reaction is named after the principal investigators of the two groups who reported it simultaneously: Zoltan Hajos and David Parrish from Hoffmann-La Roche and Rudolf Wiechert and co-workers from Schering AG. Discovered in the 1970s the original Hajos-Parrish catalytic procedure – shown in the reaction equation, leading to the optically active bicyclic ketol – paved the way of asymmetric organocatalysis. The Eder-Sauer-Wiechert modification lead directly to the optically active enedione, through the loss of water from the bicyclic ketol shown in figure.
Olfactory receptor 1A2 is a protein that in humans is encoded by the OR1A2 gene.
Olfactory receptor 5AN1 is a protein that in humans is encoded by the OR5AN1 gene.
Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction. This allows spatial information to transfer from one molecule to the target, forming the product as a single enantiomer. The chiral information is most commonly contained in a catalyst and, in this case, the information in a single molecule of catalyst may be transferred to many substrate molecules, amplifying the amount of chiral information present. Similar processes occur in nature, where a chiral molecule like an enzyme can catalyse the introduction of a chiral centre to give a product as a single enantiomer, such as amino acids, that a cell needs to function. By imitating this process, chemists can generate many novel synthetic molecules that interact with biological systems in specific ways, leading to new pharmaceutical agents and agrochemicals. The importance of asymmetric hydrogenation in both academia and industry contributed to two of its pioneers — William Standish Knowles and Ryōji Noyori — being collectively awarded one half of the 2001 Nobel Prize in Chemistry.
Chiral Lewis acids (CLAs) are a type of Lewis acid catalyst. These acids affect the chirality of the substrate as they react with it. In such reactions, synthesis favors the formation of a specific enantiomer or diastereomer. The method is an enantioselective asymmetric synthesis reaction. Since they affect chirality, they produce optically active products from optically inactive or mixed starting materials. This type of preferential formation of one enantiomer or diastereomer over the other is formally known as asymmetric induction. In this kind of Lewis acid, the electron-accepting atom is typically a metal, such as indium, zinc, lithium, aluminium, titanium, or boron. The chiral-altering ligands employed for synthesizing these acids often have multiple Lewis basic sites that allow the formation of a ring structure involving the metal atom.
Synthetic musks are a class of synthetic aroma compounds to emulate the scent of deer musk and other animal musks. Synthetic musks have a clean, smooth and sweet scent lacking the fecal notes of animal musks. They are used as flavorings and fixatives in cosmetics, detergents, perfumes and foods, supplying the base note of many perfume formulas. Most musk fragrance used in perfumery today is synthetic.
Proline organocatalysis is the use of proline as an organocatalyst in organic chemistry. This theme is often considered the starting point for the area of organocatalysis, even though early discoveries went unappreciated. Modifications, such as MacMillan’s catalyst and Jorgensen's catalysts, proceed with excellent stereocontrol.
Asymmetric addition of alkenylmetals to aldehydes is a chemical reaction in enantioselective synthesis that reacts an alkenylmetal with an aldehyde to give an allyl alcohol. The stereoselectivity in the reaction is typically controlled by the asymmetric ligands used providing a strategy to introduce controlled asymmetry into the molecule. Controlled molecular asymmetry is crucial for controlling the bioactivity of the synthesized molecules and demanded by drug authorities in drug synthesis. In this case the ligands chelate to the transition metal to create a chiral environment which enables the selective formation of a particular enantiomer. Various transition metals such as Zinc, Nickel, Chromium, and Rhodium have been used in this reaction.
In homogeneous catalysis, C2-symmetric ligands refer to ligands that lack mirror symmetry but have C2 symmetry. Such ligands are usually bidentate and are valuable in catalysis. The C2 symmetry of ligands limits the number of possible reaction pathways and thereby increases enantioselectivity, relative to asymmetrical analogues. C2-symmetric ligands are a subset of chiral ligands. Chiral ligands, including C2-symmetric ligands, combine with metals or other groups to form chiral catalysts. These catalysts engage in enantioselective chemical synthesis, in which chirality in the catalyst yields chirality in the reaction product.
Eric Block is an American chemist whose research has focused on the chemistry of organosulfur and organoselenium compounds, Allium chemistry, and the chemistry of olfaction. As of 2018, he is Distinguished Professor of Chemistry Emeritus at the University at Albany, SUNY.
