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2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (or DDQ) is the chemical reagent with formula C 6 Cl 2 (CN) 2 O 2. This oxidant is useful for the dehydrogenation of alcohols, [3] phenols, [4] and steroid ketones. [5] DDQ decomposes in water, but is stable in aqueous mineral acid. [6]
Orthogonal protection is a strategy allowing the specific deprotection of one protective group in a multiply-protected structure. For example, the amino acid tyrosine could be protected as a benzyl ester on the carboxyl group, a fluorenylmethylenoxy carbamate on the amine group, and a tert-butyl ether on the phenol
For example, (C 6 H 5)(CH 3) 2 C + is referred to as a "benzylic" carbocation. The benzyl free radical has the formula C 6 H 5 CH 2 • . The benzyl cation or phenylcarbenium ion is the carbocation with formula C 6 H 5 CH + 2 ; the benzyl anion or phenylmethanide ion is the carbanion with the formula C 6 H 5 CH − 2 .
It is also a good test for the successful deprotection of a secondary amine. Secondary amines react with chloranil to give a brown/red/orange derivative, the colour depending on the amine. In these reactions, the amine displaces chloride from the ring of the quinone.
As a second example, researchers synthesized a cycloprene-modified glutamate photocaged with a 2-nitroveratrol-based PPG. As it is an excitatory amino acid neurotransmitter, the aim was to develop a bioorthagonal probe for glutamate in vivo. [47] In a final example, Venkatesh et al. demonstrated the use of a PPG-based photocaged therapeutic. [48]
The absence of physical dividers between the sites occupied by individual oligonucleotides, a very limited space on the surface of the microarray (one oligonucleotide sequence occupies a square 25×25 μm) [107] and the requirement of high fidelity of oligonucleotide synthesis dictate the use of site-selective 5'-deprotection techniques.
1,4-Benzoquinone, commonly known as para-quinone, is a chemical compound with the formula C 6 H 4 O 2.In a pure state, it forms bright-yellow crystals with a characteristic irritating odor, resembling that of chlorine, bleach, and hot plastic or formaldehyde.
The use of N-terminal Fmoc protection allows for a milder deprotection scheme than used for Boc/Bzl SPPS, and this protection scheme is truly orthogonal under SPPS conditions. [30] Fmoc deprotection utilizes a base, typically 20–50% piperidine in DMF. [22]