| Summary: | There is much interest in the synthesis of unnatural, enantiomerically pure amino acids, including dehydroamino acids and b,b-disubstituted amino acids. Described here is a method of synthesising dehydroamino acids <i>via</i> oxazolones derived from a modified version of the Erlenmeyer reaction. (Fig. 13661A) Rh-DuPHOS and Rh-BPE hydrogenation of these dehydroamino acids led to the synthesis of single products in high d.e. and e.e. Synthesis of such oxazolones on solid phase would provide a method for on-resin amino acid modification, allowing for greater flexibility in the combinatorial synthesis of peptides. Linkage <i>via</i> a silyl linker would allow mild and selective cleavage, while use of an acid functionalised linker would allow inverse (N(r)C) peptide synthesis. Attempts to synthesise I are described, along with a method of oxazolone formation which avoids the use of acid, and is therefore compatible with silyl linkers (Fig. 13661B).
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