BOC-Amino Acids
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BOC-Amino Acids

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In nature, there are 20 kinds of natural amino acids. In recent years, many efforts have been made in the modification of amino acids, and many non-natural amino acids have been created. Non-natural amino acids play an important role in the field of proteins and peptides. BOC-amino acid is a common and typical non-natural amino acid. There are many ways to synthesize BOC-amino acids. For example, BOC amino acids are commonly used as intermediates in the synthesis of peptides. The preparation method is the reaction of 1,1,3,3-tetramethylguanidinium salts of some amino acids with tert-butyloxycarbonyl azide in 4-dimethylaminopyridine as the solvent. Also, BOC group is used as a protecting group for amines in organic synthesis.

BOC Sciences is a supplier of high-quality BOC-amino acids for research and industrial applications, with a broad selection of amino acids to meet the needs of customers in a variety of industries including pharmaceuticals, biotechnology, food and beverage. We work closely with our partners to ensure the highest quality standards, and all products are rigorously tested to ensure purity and consistency. In addition to its broad product range, BOC Sciences offers custom synthesis services for customers seeking specific amino acid derivatives or modifications. We have a team of knowledgeable and experienced employees ready to assist customers with any questions or concerns.

What is BOC in Chemistry?

Tert-butoxycarbonyl (BOC) is a widely used amino protecting group in peptide synthesis. Especially in solid-phase synthesis, Boc is used for amino protection instead of Cbz. One of the major advantages of using BOC-amino acids in solid-phase peptide synthesis is their compatibility with a variety of coupling reagents and conditions. The BOC group is stable under alkaline conditions and can perform effective coupling reactions with a variety of activating reagents. Furthermore, the BOC group can be easily removed under mild acidic conditions, making it a versatile protecting group for peptide synthesis. Boc has the following advantages:

  • Boc-amino acids can be crystallized except for a few;
  • Easy to remove by acid hydrolysis, but has certain stability;
  • Boc-amino acids can be stored for a long time without decomposing;
  • Stable to alkaline hydrolysis, hydrazinolysis and many nucleophiles;
  • Boc is stable to catalytic hydrogenolysis but is much more sensitive to acids than Cbz.

When Boc and Cbz exist at the same time, Cbz can be removed by catalytic hydrogen decomposition and Boc remains unchanged, or Boc can be removed by acid decomposition without Cbz being affected, so the two can match well.

Amino Acid Boc Protection

The free amino group can easily react with Boc2O in a mixed solvent of dioxane and water under alkaline conditions controlled by NaOH or NaHCO3 to obtain N-tert-butoxycarbonylamino compound. This is one of the common methods to introduce Boc. Its advantage is that its by-products do not interfere much and are easy to remove. Sometimes for some amines with greater nucleophilicity, they can generally react directly with Boc acid anhydride in methanol. No other base is needed, and the treatment is also convenient.

Boc protecting group

For amino derivatives that are more sensitive to water, it is better to use Boc2O/TEA/MeOH or DMF at 40-50 ℃, because these anhydrous conditions are used to protect the O17-labeled amino acids without losing O17 due to exchange with water. For sterically hindered amino acids, it is very advantageous to use Boc2O/Me4NOH·5H2O/CH3CN.

Aromatic amines generally require the addition of a catalyst due to their weak nucleophilicity. In addition, for primary amines, two Boc can be added through the use of DMAP.

Introduction of tert-butoxycarbonyl group

For amines with phenolic hydroxyl groups, the speed of attaching the phenolic hydroxyl group to Boc is also quite fast, so there is generally not much selectivity. For those with alcoholic hydroxyl groups, if DMAP is used as a catalyst, the alcoholic hydroxyl groups can also be bound to Boc after a long time, so the reaction should not be carried out overnight.

Sterically hindered amines tend to react with Boc2O to form urea due to the formation of cyanate esters. This problem can be avoided by reacting the amine NaH or NaHMDS (sodium hexamethyldisilazonium) and then reacting it with Boc2O.

Sometimes, more Boc acid anhydride may be added during the reaction. When there is no free acid and base in the molecule, it is difficult to get out. If it must be removed, some N,N-dimethylethylenediamine or N,N-dimethylpropanediamine is generally added to the system, and then the N,N-dimethylethylenediamine or N,N-dimethylpropanediamine on the Boc is removed with dilute acid.

Amino Acid Boc Deprotection

Boc is more sensitive to acid than Cbz, and the acid decomposition products are isobutylene and CO2. In liquid phase peptide synthesis, Boc can generally be removed using TFA or 50% TFA (TFA:CH2Cl2 = 1:1, v/v). In solid-phase peptide synthesis, since TFA will bring some side reactions (such as adding a trifluoroacetyl group on the obtained amine, etc.), 1-2M HCl/organic solvent is often used. Generally speaking, HCl/dioxane is more common.

Deprotection boc group

In addition to removing Boc, Me3SiI can also cleave carbamates, esters, ethers and ketals in CHCl3 or CH3CN under neutral anhydrous conditions. A certain selectivity can be achieved by controlling conditions.

When there are some functional groups in the molecule that can react with the by-product tert-butyl carbocation under acidic conditions, thiophenol (such as thiophenol) needs to be added to remove tert-butyl carbocation. This prevents alkylation of methionine and tryptophan during de-Boc. Other scavengers may also be used, such as anisole, thiomethyl ether, cresylthiophenol, cresol and dimethyl sulfide. TBDPS (tert-butyldiphenylchlorosilane) and TBDMS (tert-butyldimethylsilyl) groups are stable to CF3COOH during Boc removal. In the presence of primary amine derivatives, ZnBr2/CH2Cl2 can selectively remove Boc from secondary amines.

What Do BOC-Amino Acids Do?

BOC-amino acids are versatile tools for peptide synthesis with wide applications in organic chemistry, biochemistry and pharmaceuticals. Their ease of use, compatibility with a wide range of chemical reactions, and ability to improve the properties of amino acids make them a valuable resource for researchers working on peptide and protein development. As peptide synthesis and drug development continue to advance, BOC-amino acids may remain an important tool for the synthesis of complex peptides and proteins in the future.

  • Peptide Synthesis

The BOC protecting group is a bulky sterically hindered group that can be easily removed under mild conditions, making it a versatile tool for peptide synthesis. BOC groups are typically introduced into amino acid side chains by reacting the amino acid with BOC anhydride in the presence of a base such as triethylamine. The BOC group can then be removed using a weak acid such as trifluoroacetic acid (TFA) to expose the free amino group for further chemical reactions.

One of the main advantages of using BOC-amino acids in peptide synthesis is their compatibility with a wide range of chemical reactions. BOC protecting groups are stable to the most common reagents and conditions used in peptide synthesis, allowing selective deprotection of amino groups without affecting other functional groups on the amino acid side chains. This makes BOC-Amino Acids a valuable tool for the synthesis of complex peptides and proteins with multiple amino acid residues. Another advantage of using BOC-amino acids in peptide synthesis is the ease of purification. The BOC group is easily removed under mild acidic conditions, allowing isolation of the desired peptide product without extensive purification steps. This saves time and resources in peptide and protein synthesis, making BOC-amino acids a cost-effective option for researchers in the fields of biochemistry and organic chemistry.

  • Pharmaceutical Preparation

In addition to their use in peptide synthesis, BOC-amino acids are also used in the development of pharmaceutical and biotechnological products. BOC protecting groups can be used to modify the properties of amino acids, such as solubility and stability, to improve the bioavailability and efficacy of peptide drugs. BOC-amino acids have been used in the synthesis of a variety of drugs, including antibiotics, antivirals, and anticancer drugs.

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