Application of the Lossen rearrangement to the synthesis of N-urethane protected a-peptidyl ureas and ureidopeptides is reported. The carbodiimide mediated rearrangement of N-Boc/Z/Fmoc protected a-amino/peptide hydroxamic acids into isocyanates and coupling of the latter with the amino acid esters/peptide esters have been accomplished in a single-pot to obtain good yields of urea products. Synthesis of the ureidoalanine derivatives via the hydroxamate derivatives of N-protected aspartic acid has also been carried out using the same procedure.
Abstract-An efficient synthesis of tetrazole analogues of amino acids starting from N a -Fmoc amino acid in a three-step protocol is reported. The free amino tetrazoles were obtained in good yields and with excellent purity after removal of the Fmoc group. The synthesis of analogues of aspartic and glutamic acids in which the 5-tetrazolyl moiety is inserted at the b/c carboxyl group starting from Fmoc-Asn and Fmoc-Gln and the incorporation of these tetrazoles into peptides are also described.
An epimerization free and efficient total synthesis of immunosuppressant cyclosporin O (CsO) by step-by-step assembly of amino acids in solution phase is reported. The couplings were performed by employing Fmoc-amino acid chlorides and were mediated by zinc dust under neutral conditions. The yield and purity of the coupling of sterically hindered N-methylamino acids to N-methylamino acids at positions 8, 9, 10, and 11 were enhanced by repeating the coupling thrice at these particular junctures. All the 10 intermediate peptides pertaining to CsO and the final CsO were isolated and completely characterized through IR, 1H NMR, mass spectrometry, and HPLC techniques.
a b s t r a c tIsoselenocyanates derived from Boc/Z-amino acids are prepared by the reaction of the corresponding isonitriles with selenium powder in presence of triethylamine at reflux. The utility of these new classes of isoselenocyanates in the preparation of selenoureidodipeptidomimetics possessing both amino as well as carboxy termini has been accomplished. The 1 H NMR analysis confirmed that the protocol involving the conversion of isonitriles to isoselenocyanates and their use as coupling agents in assembling selenoureido derivatives is free from racemization.
Diphenylphosphoryl azide (DPPA) mediated one-pot synthesis of N a -Fmoc/Bsmoc/Boc/Z-protected ureidopeptides and peptidyl ureas as well as phenyl/succinimidyl (N a -urethane protected) methyl carbamates starting from N a -protected amino acids is reported. The formation of an azide, its rearrangement and coupling with an amino component is accomplished in a sequence of one-pot operations. The protocol has incorporated urea linkages in a sterically hindered peptide.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.