The ball-milling technique was used under solvent-free conditions to perform a Horner-Wadsworth-Emmons reaction in the presence of a mild carbonate base. Starting from a phosphonate-substituted glycine, this method gave access to Boc-protected unsaturated amino esters in excellent yield and selectivity in many cases. The scope of the reaction was delineated.
A new linker cis-5-aminopent-3-enoic acid (cis-Apa) was prepared for the synthesis of cyclic pseudopeptides by cyclization-cleavage by using ring-closing methatesis (RCM). We developed a new synthetic pathway for the preparation of the cis-Apa linker that was tested in the cyclization-cleavage process of different RGD peptide sequences. Different macrocyclic peptidomimetics were prepared by using this integrated microwave-assisted method, showing that the readily available cis-Apa amino acid is well adapted as a linker in the cyclization-cleavage process.
Solvent-Free Synthesis of Unsaturated Amino Esters in a Ball-Mill. -Horner-Wadsworth-Emmons reaction of phosphonate (I) with aldehydes is successfully achieved in the presence of a mild carbonate base to give the (Z)-isomers as sole or main products. Ketones do not react. -(BARON, A.; MARTINEZ, J.; LAMATY*, F.; Tetrahedron Lett. 51 (2010) 48, 6246-6249, http://dx.
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