Target-oriented synthesis 3-amino acids

Nucleophilic 1,4- and 1.6-additions of cuprates and other organometallic reagents to acceptor-substituted dienes have been utilized extensively in target-oriented stereoselective synthesis - . Schollkopf and coworkers reported the diastereoselective 1,6-addition of a bislactim ether-derived cuprate to 3,5-heptadien-2-one (90% ds equation 17). The corresponding reactions of dienoates were conducted with the lithiated bislactim ether and proceeded with diastereoselectivities of >99% ds (equation 18) the adducts could be converted easily into diastereo- and enantiomerically pure amino acid derivatives. 

Contrary to the principles of the ribosomal protein biosynthesis, where the carboxylic functions of amino acids are reactively bound to a polymer — the transfer ribonucleic acid (t-RNA) — which itself is orientated specifically on the ribosomal messenger ribonucleic acid (m-RNA) (Fig. 1 for details see [36]), the basic idea of the Merrifield synthesis depends upon a nonreactive covalent fixation of the C-terminal amino acid of the target peptide on a solid support (Fig. 2). On this insoluble but swollen polymer, the pep-... 

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