Proline chimeras

The zinc-enolate carbocyclization reaction was applied to the synthesis of diverse 3-substituted proline chimeras. To this end, the stable cyclic organozinc intermediate... 

Karoyan et al. accomplished an asymmetric synthesis of prolino-homotrypto-phan 50 via amino-zinc-ene-enolate cyclization of 47 followed by transmetalation of the cyclic zinc intermediate 48 with indolyliodide 49 [84]. The use of a Pd catalyst derived from Fu s [f-BusPHj-BFa was required to avoid the undesired p-hydride elimination. Proline chimeras such as 50 are useful tools for medicinal chemistry and/or biological applications. 

Peptide nucleic acid (PNA) has received considerable attention for several years as a candidate for antisense exploitation. Several publications have addressed the physical and biological properties, applications and characterisation of PNA and modified PNAs. One problem associated with PNA is its poor solubility. There has therefore been interest in the synthesis of mixed PNA-DNA chimeras " and the introduction of charge into the PNA monomer itself. Phosphonate PNA 157a has been prepared using the aminomethylpho-sphonate 157b. Proline derived PNA monomers 158 have been described. ... 

A further investigated group of local constraints are derivatives of the natural amino acids proline. Proline analogs displaying the characteristics of other amino acids are referred to as proline-amino acid chimeras, and have been used to study the spatial requirements for receptor affinity and biological activity of both natural amino acids and peptides. For example, p-substituted-prolines such as 3-carboxyproline, 3-phenylproline, and 3-di-methylproline combine amino acid side chain functionality with proline s conformational... 

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