Proteins are made from repeating amino acid units, and sugars are made from repeating monosaccharide units. The connections are 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 a series of reactions each requiring only a small energy step. Mimicking nature in organic synthesis is essential in the discovery of new pharmaceuticals 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 fewer 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, is stable at room temperature, and does not react with 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.
Many of the Click chemistry criteria are subjective, and even if measurable and objective criteria could be agreed upon, it is unlikely that any reaction will be perfect for every situation and application. However, several reactions have been identified that fit the concept better than others:
- cycloadditions, such as the Huisgen 1,3-dipolar cycloaddition, in particular the Cu(I)-catalyzed stepwise variant, are often referred to simply as Click reactions
- thiol-ene click reactions
- Diels-Alder reaction and inverse electron demand Diels-Alder reaction
- cycloadditions between isonitriles (isocyanides) and tetrazines
- nucleophilic substitution especially to small strained rings like epoxy and aziridine compounds
- carbonyl-chemistry-like formation of ureas but not reactions of the aldol type due to low thermodynamic driving force.
- addition reactions to carbon-carbon double bonds like dihydroxylation or the alkynes in the thiol-yne reaction.
Read more about this topic: Click Chemistry
Other articles related to "explanation, explanations":
... In such cases, comments may contain an explanation of the methodology ... Such explanations may include diagrams and formal mathematical proofs ... This may constitute explanation of the code, rather than a clarification of its intent but others tasked with maintaining the code base may find such explanation crucial ...
... There are many and varied events, objects, and facts which require explanation ... So too, there are many different types of explanation ... Aristotle recognized at least four types of explanation ...
... "Explanation" is a poem from Wallace Stevens's first book of poetry, Harmonium (1923) ... Explanation Ach, Mutter, This old, black dress, I have been embroidering French flowers on it ... on the church-wall This poem may be an explanation of the difference between conventional decoration and artistic imagination, the latter represented, as Buttel proposes, by an ...
... part of this lecture is devoted to Eliot's critique of what he calls "the criticism of explanation by origins" (107) ... of Finnegans Wake in order to illuminate the distinction between explanation and understanding ...
Famous quotes containing the word explanation:
“There is a great deal of unmapped country within us which would have to be taken into account in an explanation of our gusts and storms.”
—George Eliot [Mary Ann (or Marian)
“The explanation of the propensity of the English people to portrait painting is to be found in their relish for a Fact. Let a man do the grandest things, fight the greatest battles, or be distinguished by the most brilliant personal heroism, yet the English people would prefer his portrait to a painting of the great deed. The likeness they can judge of; his existence is a Fact. But the truth of the picture of his deeds they cannot judge of, for they have no imagination.”
—Benjamin Haydon (17861846)
“There is no explanation for evil. It must be looked upon as a necessary part of the order of the universe. To ignore it is childish, to bewail it senseless.”
—W. Somerset Maugham (18741965)