Chiral Auxiliary

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Chiral Auxiliary

Chiral auxiliary is a compound or unit that is temporarily added to organic synthesis in order to control the synthesis of stereochemistry. As the figure below shows, by adding the chiral auxiliary, the prochiral substrate can be transformed into a chiral product. Moreover, through an auxiliary recycle, the auxiliary can be typically recovered for future use. As an auxiliary for chiral synthesis, it must have the following conditions: the synthesis procedure must be highly stereoselective; if used as raw material, the newly generated chiral center or other chiral elements should be easily separated from chiral auxiliary without racemization; it has high recovery without reducing the optical purity.

Chiral Auxiliary Fig 1. The mechanism model of chiral auxiliary

Below is a list of our available chiral auxiliaries (include but not limited to the following):

Menthol

phenylmenthol Menthol can be used to prepare the key prostaglandin intermediate in optically pure form without resolution, such as 8-phenylmenthol. It is proposed that the back face of the acrylate is blocked by the auxiliary, so that cycloaddition occurs at the front face of the olefin.

Chiral Auxiliary Fig 2 The synthesis of intermediate of prostaglandin using 8-phenylmenthol

Oxazolidinone auxiliaries, popularized by David Evans, have been applied to many stereoselectivity conversions, including the aldol reactions, alkylation reactions, and Diels-Alder reactions. Usually, the acid chloride substrate reacts with the oxazolidinone to form an imide. Substituents at the 4 and 5 positions of the oxazolidinone direct any aldol reaction to the alpha position of the carbonyl of the substrate. We can provide several available oxazolidinone chiral auxiliaries, including the three below.

Chiral Auxiliary

Enantiomerically pure sulfoxides can be efficient chiral controllers, which is cheap and easy to introduce and functionalize. Therefore, they are versatile intermediates for a number of organic reactions. Introduction of the sulfinyl group mostly occurs by nucleophilic addition of the deprotonated sulfoxide to an ester to form β-keto sulfoxides.

(S)-1-amino-2-methoxymethylpyrrolidine (SAMP) and (R)-1-amino-2-methoxymethylpyrrolidine (RAMP) have become commonly used chiral auxiliaries for organic synthesis. The auxiliary SAMP is available in four steps starting from (S)-proline, RAMP can be synthesized in six steps from glutamic acid.

Amino alcohols are important chiral auxiliaries to form chelates. Ephedrine derivatives are especially popular in this respect. The asymmetric alkylation of substrates attached to pseudoephedrine is a highly efficient method for the synthesis of optically active carboxylic acids or amino acids.

Both enantiomeric forms of camphor are commercially available and inexpensive. Its rigid backbone is an attractive structural element for chiral auxiliaries. As a consequence, many structurally diverse camphor-derived auxiliaries have been prepared in only a few steps as well as successfully employed in a variety of different reactions.

The attractiveness of carbohydrate-derived auxiliaries results from the fact that they bear many stereocenters and are often commercially available and reasonably priced. They have been successfully employed in numerous organic reactions, such as cycloadditions (Diels–Alder reactions, [2+2] cycloadditions), cyclopropanations, alkylations, and Mannich reactions.

Experts with extensive experience in chiral auxiliaries synthesis in BOC Sciences can help provide pure optical chiral auxiliaries with the advantages mentioned above to meet your specific needs. We also use multiple techniques (NMR, LCMS, GCMS, X-ray) to analyze compounds after the chiral synthesis completed. If you have any chiral auxiliaries synthesis requirement in mind, please do not hesitate to contact us. We will endeavor to provide highly satisfying products and services!

Reference

  1. Gnas Y., Glorius, F.; et al. Chiral auxiliaries-principles and recent applications Cheminform.2006, 3: 1899-1930.
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