An improved approach for the synthesis of α,α-dialkyl glycine derivatives by the Ugi–Passerini reactionElectronic supplementary information (ESI) available: spectroscopic data for compounds 1-5. See http://www.rsc.org/suppdata/ob/b2/b212473b/
An improved approach for the synthesis of α,α-dialkyl glycine derivatives by the Ugi–Passerini reactionElectronic supplementary information (ESI) available: spectroscopic data for compounds 1-5. See http://www.rsc.org/suppdata/ob/b2/b212473b/
Several fully protected tri- and pentapeptides containing a central symmetrical alpha,alpha-dialkyl glycine residue, with the alkyl group varying from methyl or ethyl to benzyl, were synthesized in good yields by a strategy based on the Ugi-Passerini reaction. Each Ugi-Passerini adduct was selectively cleaved and the product submitted to an assisted N,N'-dicyclohehylcarbodiimide coupling to an amino acid or dipeptide ester, respectively. Tripeptides as the above but containing a 4-methoxybenzyl group at the nitrogen atom of the central residue were also synthesized in fair to good yields by N-[(1H-benzotriazol-1-yl)(dimethylamino)methylene]-N-methylmethanaminium hexafluorophosphate N-oxide assisted couplings. The results reported here show that our strategy is appropriate for routine synthesis of peptides incorporating these moieties. (C) 2009 Elsevier Ltd. All rights reserved.