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Synthesis 2008(3): 438-444  
DOI: 10.1055/s-2008-1032029
PAPER
© Georg Thieme Verlag Stuttgart · New York

Carbamoyl Azides of α-N-Protected Amino Acids: A Fast and Simple One-Pot Synthesis

Giancarlo Verardo*, Elisa Bombardella, Paola Geatti, Paolo Strazzolini
Department of Chemical Sciences and Technologies, University of Udine, Via del Cotonificio 108, 33100 Udine, Italy
Fax: +39(0432)558803; e-Mail: giancarlo.verardo@uniud.it;
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Publication History

Received 10 October 2007
Publication Date:
10 January 2008 (online)

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Abstract

A fast and simple one-pot synthesis of carbamoyl azides of α-N-protected amino acids is reported. The procedure involves the reaction between sodium azide and the mixed anhydride obtained from an α-N-protected amino acid and isobutyl chloroformate, in the presence of KH2PO4. The reaction rate was influenced by the nature of both the α-N-protection and the amino acid side chain. Surprisingly, tert-butyloxycarbonyl (α-N-Boc) and benzyl­oxycarbonyl (α-N-Cbz) protected proline afforded the corresponding isocyanates instead of the expected carbamoyl azides.

Key words

α-N-protected amino acids - sodium azide - carbamoyl azide - mixed anhydride - Curtius rearrangement