Homodet cyclic peptides

Cyclic dipeptides, bearing the DKP ring, in which the amide linkages are cis, are known to represent the simplest form of homodetic cyclic peptides. ... 

Cyclic peptides in which the ring consists solely of aminoacid residues with eupeptide links may be called homodetic cyclic peptides. Three representations are possible. Gramicidin S is given as an example. In this decapeptide, all amino acids are l, with the exception of Phe which is d, as is shown by o-Phe or oPhe. 

Homodetic cyclic peptides are classified according to the location of the ring juncture as shown in Scheme 1. The most common mode of cyclization is head-to-tail where ring closure occurs by amide bond between the N-terminal amino group and the C-terminal carboxy group. Additional ring closures involve side-chain functionalities such as head-to-side-chain, side-chain-to-side-chain or side-chain-to-tail cyclizations. Moreover, in backbone cycliza-tions 29 (see Section 6.8.3.2.4) the backbone amides may be linked to a second backbone amide or to side chains as well as to the termini of the peptide. 

In addition to homodetic cyclic peptides, chemical ligation methods have been developed that lead to heterodetic cyclic peptides containing thiazolidine. 158-161 ... 

Synthesis of Homodetic Cyclic Peptides on Solid Support... 

Blaha, K. Linear Peptides Synthetic Methods Wade, R. Linear Peptides Synthesis and Structure — Activity Relationships Wieland, T., Birr, C. Homodetic Cyclic Peptides, in Amino Acids, Peptides and Related Compounds, International Review of Science, Vol. 6 (ed. Rydon, H. N.), p. 73, 97, 183, Butterworths, London 1976... 

The oxime resin 5z [255,256], which forms an acid-stable anchor for the carboxyl group of amino acids, has been used for some time for the synthesis of C-terminal modified peptides and homodetic cyclic peptides. The key step in lactam formation is intramolecular nucleophilic attack of the A-terminus at the anchoring group. The resin also reacts with isocyanates and the products undergo nucleophilic attack by amines resulting in the release of ureas [257], Resin-bound Boc-tryptophan has been used in the acid-catalyzed Pictet-Spengler synthesis with final products cleaved as primary amides by... 

Scheme 1 Topological subclasses of homodetic cyclic peptides.

A special class of homodetic cyclic peptides was introduced by Gilon et al. 

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