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Synthetic studies on threonines. The preparation of protected derivatives of d-allo- and l-allo-threonine for peptide synthesis

✍ Scribed by Paul Lloyd-Williams; Agustí Sánchez; Natàlia Carulla; Teresa Ochoa; Ernest Giralt

Publisher
Elsevier Science
Year
1997
Tongue
French
Weight
853 KB
Volume
53
Category
Article
ISSN
0040-4020

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✦ Synopsis

N-Acetylated threonine derivatives, having tert-butyl or benzyl-based side-chain protection, form isolable 5(4H)-oxazolones on treatment with N-ethyl-N'-3-dimetlaylaminopropyl carbodiimide. N-chloroacetylated threonine derivatives, on the other hand, do not form oxazolones so readily. The N-acetylated oxazolones are easily epimerized and lead to diastereoisomeric mixtures of threonine derivatives on hydrolysis with dilute aqueous acid. The components of these mixtures can be separated chromatographically, but a useful alternative for the O-benzylated mixture is selective enzymatic hydrolysis using hog kidney acylase. These chemical transformations provide the basis for practical syntheses of protected derivatives of the non-proteinogenic allo-threonines, suitable for use in peptide synthesis.

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Simple methods for the preparation of protected derivatives of d-allo- and l-allo-threonine
✍ Paul Lloyd-Williams; Natàlia Carulla; Ernest Giralt 📂 Article 📅 1997 🏛 Elsevier Science 🌐 French ⚖ 235 KB

Practical syntheses of protected derivatives of the non-proteinogenic allo-threonines are decribed. The key step is enzymatic resolution of threonine diastereomers, produced on controlled epimerization of the a-carbon atom. The protected allo-threonines are obtained in good overall yield and can be