What is protecting group in organic synthesis?
Protecting Groups in Organic Synthesis. What is a protecting group? A protecting group (PG) is a molecular framework that is introduced onto a specific functional group (FG) in a poly-functional molecule to block its reactivity under reaction conditions needed to make modifications elsewhere in the molecule.
What is the purpose of a protecting group in organic chemistry?
Protecting groups are used in synthesis to temporarily mask the characteristic chemistry of a functional group because it interferes with another reaction. A good protecting group should be easy to put on, easy to remove and in high yielding reactions, and inert to the conditions of the reaction required.
What are orthogonal protecting groups?
The presence of both protective groups in the same molecule therefore enables selective deprotection of one protected amino group for a further reaction while the second protected amino group remains untouched. This is referred to as an orthogonal protecting group strategy.
How can we protect amine groups?
The most popular choice of protecting group for amine nitrogen is the carbamate functional group….The nitrogen of a carbamate is relatively non-nucleophilic, and furthermore, carbamates are:
- easily installed on nitrogen.
- inert to a wide variety of reaction conditions.
- easily removed without affecting existing amide groups.
What are protecting groups give examples?
Common protecting groups
- Acetyl (Ac) – Removed by acid or base (see Acetoxy group).
- Benzoyl (Bz) – Removed by acid or base, more stable than Ac group.
- Benzyl (Bn) – Removed by hydrogenolysis.
- β-Methoxyethoxymethyl ether (MEM) – Removed by acid.
What is meant by protecting groups?
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis.
How can we protect the alkene groups?
The presence of a bromide substituent, instead of a hydrogen or methyl group, on a carbon–carbon double bond, protects the alkene from addition reactions when exposed to trifluoroacetic acid.
What is the role of protective groups in protein synthesis?
Protecting group strategies are usually necessary to prevent undesirable side reactions with the various amino acid side chains. Chemical peptide synthesis most commonly starts at the carboxyl end of the peptide (C-terminus), and proceeds toward the amino-terminus (N-terminus).
How can we protect carbonyl group?
Protection of carbonyl groups:
- Acetals and Ketals – Removed by acid. Normally, the cleavage of acyclic acetals is easier than of cyclic acetals.
- Acylals – Removed by Lewis acids.
- Dithianes – Removed by metal salts or oxidizing agents.
How can we protect ketone groups?
Cyclic acetals and ketals are the most useful carbonyl (aldehyde or ketone) protecting groups. Common diols used to form ketals are show below in order of their relative rate of formation. 1,3-dioxanes cleave faster than 1,3-dioxolanes. Acetals and ketals are easily formed and cleaved.
How can we protect alcohol groups?
The most common protecting groups for alcohols are the silyl ethers. Here is the idea behind it. We take a silyl chloride, do a substitution using the alcohol as a nucleophile and then the alcohol converted into a silyl ether can be used in the presence of any strong base including the Grignard reagent.
How can we protect the OH group of alcohol?
In the case of alcohols the hydroxyl group may be protected by formation of an ether, an ester, or an acetal.
