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Information about Click Chemistry

Click chemistry is a chemical philosophy introduced by K. Barry Sharpless in 2001 and describes chemistry tailored to generate substances quickly and reliably by joining small units together. This is inspired by the fact that nature also generates substances by joining small modular units.

Explanation

In biochemistry, proteins are made from repeating amino acid units and sugars are made from repeating monosaccharide units. The connecting units are based on carbon - hetero atom bonds C-X-C rather than carbon - carbon bonds. In addition, enzymes ensure that chemical processes can overcome large enthalpy hurdles by division into a series of reactions each with a small energy step. Mimicking nature in organic synthesis of new pharmaceuticals is essential given the large number of possible structures.

In 1996 Guida calculated the size of the pool of drug candidates at 1063, based on the presumption that a candidate consists of less than 30 non-hydrogen atoms, weighs less than 500 daltons, is made up of atoms of hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, chlorine and bromine, and is stable at room temperature and stable towards oxygen and water. Click chemistry in combination with combinatorial chemistry, high-throughput screening and building chemical libraries speeds up new drug discoveries by making each reaction in a multistep synthesis fast, efficient and predictable.

Click chemistry encourages the following criteria:
  • application modular and wide in scope
  • obtains high chemical yield
  • generates inoffensive byproducts
  • is stereospecific
  • simple reaction conditions
  • has readily available starting materials and reagents
  • no solvent involved or a benign solvent (preferably water)
  • easy product isolation by crystallisation or distillation but not preparative chromatography
  • physiologically stable
  • large thermodynamic driving force > 84 kJ/mol to favor a reaction with a single reaction product. A distinct exothermic reaction makes a reactant "spring loaded".
  • high atom economy
Many of the criteria are subjective; and even if measurable and objective criteria could be agreed upon, it's unlikely that any reaction will be perfect for every situation and application. However, several reactions have been identified which fit the bill better than others:
  • The Huisgen 1,3-dipolar cycloaddition, in particular the Cu(I)-catalyzed stepwise variant, is often referred to simply as the "click reaction". The Cu(I)-catalyzed variant was first reported by Morten Meldal and co-workers from Carlsberg Laboratory, Denmark for the synthesis of peptidotriazoles on solid support. Fokin and Sharpless independently described it as a reliable catalytic process offering "an unprecedented level of selectivity, reliability, and scope for those organic synthesis endeavors which depend on the creation of covalent links between diverse building blocks", firmly placing it among the most reliable processes fitting the click criteria.
  • Other cycloadditions such as the Diels-Alder reaction
  • nucleophilic substitution especially to small strained rings like epoxy and aziridine compounds
  • carbonyl-chemistry-like formation of ureas and amides but not reactions of the aldol type due to low thermodynamic driving force.
  • addition reactions to carbon — carbon double bonds like epoxidation and dihydroxylation.

References

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Chemistry
Analytical chemistry • Biochemistry • Bioinorganic chemistry • Chemical biology • Chemistry education • Click chemistry • Cluster chemistry • Computational chemistry • Electrochemistry • Environmental chemistry • Green chemistry • Inorganic chemistry • Materials science • Medicinal chemistry • Nuclear chemistry • Organic chemistry • Organometallic chemistry • Pharmacy • Pharmacology • Physical chemistry • Photochemistry • Polymer chemistry • Solid-state chemistry • Supramolecular chemistry • Theoretical chemistry • Thermochemistry • Wet chemistry
List of biomolecules • List of inorganic compounds • List of organic compounds • Periodic table
Karl Barry Sharpless (born April 28, 1941) is an American chemist known for his work on organometallic chemistry.

In 2001 he won the Nobel Prize in Chemistry for his work on stereoselective oxidation reactions (Sharpless epoxidation, Sharpless asymmetric dihydroxylation,
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Nature, in the broadest sense, is equivalent to the natural world, physical universe, material world or material universe. "Nature" refers to the phenomena of the physical world, and also to life in general.
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Biochemistry is the study of the chemical processes in living organisms.[1] The word "biochemistry" comes from the Greek word βιοχημεία biochēmeia, which means "the chemistry of life.
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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amino acid is a molecule that contains both amine and carboxyl functional groups. In biochemistry, this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent.
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Monosaccharides (from Greek : single, sacchar: sugar) are the simplest carbohydrates. They cannot be hydrolyzed into simpler sugars. They consist of one sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste.
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In the nomenclature of organic chemistry, a heteroatom (from Ancient Greek heteros, different, + atomos) is any atom that is not carbon or hydrogen. It is typically, but not exclusively, nitrogen, oxygen, sulfur, phosphorus, boron, chlorine, bromine, or iodine.
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Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions.[1] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products.
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In thermodynamics and molecular chemistry, the enthalpy or heat content (denoted as H or ΔH, or rarely as χ) is a quotient or description of thermodynamic potential of a system, which can be used to calculate the "useful" work
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The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic and molecular masses. It is defined to be one twelfth of the mass of an unbound atom of the carbon-12 nuclide, at rest and in its ground state.
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1, −1
(amphoteric oxide)
Electronegativity 2.20 (Pauling scale) More

Atomic radius 25 pm
Atomic radius (calc.) 53 pm
Covalent radius 37 pm
Van der Waals radius 120 pm
Miscellaneous

Thermal conductivity (300 K) 180.
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4, 2
(mildly acidic oxide)
Electronegativity 2.55 (Pauling scale)
Ionization energies
(more) 1st: 1086.5 kJmol−1
2nd: 2352.6 kJmol−1
3rd: 4620.5 kJmol−1

Atomic radius 70 pm
Atomic radius (calc.
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3, 5, 4, 2
(strongly acidic oxide)
Electronegativity 3.04 (Pauling scale)
Ionization energies
(more) 1st: 1402.3 kJmol−1
2nd: 2856 kJmol−1
3rd: 4578.1 kJmol−1

Atomic radius 65 pm
Atomic radius (calc.
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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5, 4
(mildly acidic oxide)
Electronegativity 2.19 (Pauling scale)
Ionization energies
(more) 1st: 1011.8 kJmol−1
2nd: 1907 kJmol−1
3rd: 2914.1 kJmol−1

Atomic radius 100 pm
Atomic radius (calc.
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6
(strongly acidic oxide)
Electronegativity 2.58 (Pauling scale)
Ionization energies
(more) 1st: 999.6 kJmol−1
2nd: 2252 kJmol−1
3rd: 3357 kJmol−1

Atomic radius 100 pm
Atomic radius (calc.
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1, 3, 5, 7
(strongly acidic oxide)
Electronegativity 3.16 (Pauling scale)
Ionization energies
(more) 1st: 1251.2 kJmol−1
2nd: 2298 kJmol−1
3rd: 3822 kJmol−1

Atomic radius 100 pm
Atomic radius (calc.
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Bromine (IPA: /ˈbroʊmiːn, ˈbroʊmaɪn, ˈbroʊmɪn/, Greek: βρῶμος, brómos, meaning "stench (of he-goats)"
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Room temperature (also referred to as ambient temperature) is a common term to denote a certain temperature within enclosed space at which human beings are accustomed.
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Combinatorial chemistry involves the rapid synthesis or the computer simulation of a large number of different but structurally related molecules.

Introduction

Synthesis of molecules in a combinatorial fashion can quickly lead to large numbers of molecules.
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High-throughput screening (HTS), is a method for scientific experimentation especially used in drug discovery and relevant to the fields of biology and chemistry.

Purpose and method


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A chemical library or compound library is a collection of stored chemicals usually used ultimately in high-throughput screening or industrial manufacture. The chemical library can consist in simple terms of a series of stored chemicals.
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In chemistry, Yield, also referred to as chemical yield and reaction yield, is the amount of product obtained in a chemical reaction.[1] The absolute yield can be given as the weight in grams or in moles (molar yield).
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In chemistry, stereospecificity is the property of a chemical reaction that yields different stereoisomeric reaction products from two stereoisomeric reactants depending on the reaction conditions.
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A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. The most common solvent in everyday life is water. Most other commonly-used solvents are organic (carbon-containing) chemicals. These are called organic solvents.
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Crystallization is the (natural or artificial) process of formation of solid crystals from a uniform solution. Crystallization is also a chemical solid-liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.
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Distillation is a method of separating chemical substances based on differences in their volatilities in a boiling liquid mixture. Distillation usually forms part of a larger chemical process, and is thus referred to as a unit operation.
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Chromatography (from Greek χρώμα:chroma, colour and γραφειν:"grafein" to write) is the collective term for a family of laboratory techniques for the separation of mixtures.
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The joule (IPA: [dʒuːl] or [dʒaʊl]) (symbol: J) is the SI unit of energy.
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