A. Heydari, Roohollah Kazem Shiroodi, H. Hamadi
Aug 13, 2007
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0
Influential Citations
46
Citations
Journal
Tetrahedron Letters
Abstract
Abstract—The commercially available heteropoly acid H 3 PW 12 O 40 (0.5 mol %) is a very efficient and environmentally benign cat-alyst for N-tert-butoxycarbonylation of amines (primary, secondary) with di-tert-butyl dicarbonate at room temperature in shortreaction times (<10 min). No competitive side products such as isocyanates, ureas, N,N-di-tert-butoxycarbonyls, O-Boc and oxazol-idinones were observed. Chiral a-amino alcohols and esters afforded the corresponding N-Boc derivatives chemoselectively in excel-lent yields. 2007 Elsevier Ltd. All rights reserved. 1. IntroductionAs N-tert-butoxycarbonyl amino acids are resistant toracemization during peptide synthesis, the N-Boc moietyis one of the most important amine protecting groups. 1,2 The tert-butoxycarbonyl group is cleaved withCF 3 CO 2 H in 5–10 min at room temperature. Cheaperacids such as 3 M HCl in EtOAc or 10% H 2 SO 4 in diox-ane or hot formic acid can be considered for large scaledeprotection. N-Boc-protected amino acids can easilybe converted into the free amine and are useful in Merri-field’s solid phase peptide synthesis. The stability of N-Boctocatalytichydrogenationanditsresistancetowardsbasic and nucleophilic attack make carbamates andbenzyl esters ideal orthogonal partners for protection ofamines during the synthesis of multifunctional targets.