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A concise and scalable route to L-azidohomoalanine


A concise and highly efficient synthetic route to L-azidohomoalanine (L-Aha) and its homologues is presented here. These chemically modified amino acids are used for the introduction of bioorthogonal handles into proteins. The described route avoids major problems of previously reported methods including expensive starting materials, low efficiency, and lack of scalability. Starting from inexpensive N-Boc-O-Bn-L-aspartic acid, gram quantities of L-Aha hydrochloride can be prepared with high purity. The reactions can be completed within 1 week and the products can be incorporated into proteins using L-methionine auxotrophs.

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Figure 1: Small- and large-scale preparation of L-Aha.


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We thank the Biotechnology and Biosciences Research Council (BBSRC) (BBE0140891) and Medical Research Council (MRC) (G0801741) for funding this project. The thermogravimetric analysis and dynamic scanning calorimetry measurements on L-Aha were conducted by E. Greenhalgh under the supervision of D. Irvine at the University of Nottingham.

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Authors and Affiliations



S.R. conducted the initial syntheses and determined the synthetic routes as well as prepared the first draft of the manuscript. W.C.D. repeated and refined the syntheses; he also modified the reaction conditions and reagents for several steps to improve yields when conducting the reactions on a larger scale. He was also involved in manuscript preparation. N.R.T. supervised all of the work and prepared the final version of the manuscript.

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Correspondence to Neil R Thomas.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Data 1

1H NMR spectrum of L-Aha·HCl. (PDF 21 kb)

Supplementary Data 2

13C NMR spectrum of L-Aha·HCl. (PDF 34 kb)

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Roth, S., Drewe, W. & Thomas, N. A concise and scalable route to L-azidohomoalanine. Nat Protoc 5, 1967–1973 (2010).

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