Phosphines peptide-bound

The method of esterification, based on the double activation route to macro-lides, mentioned earlier (Scheme 26, p. 135) has been found to be equally effective in the formation of amides from carboxylic acids and primary or secondary amines. The well known method for amide bond formation in peptide synthesis using mixtures of triphenylphosphine and 2,2 -dipyridyl disulphide has been modified by employing polymer-bound triphenylphosphine. In a similar vein, mixtures of triphenylphosphine and carbon tetrachloride have been reported to be useful in the formation of amide linkages in peptide synthesis.A similar method using polymer-bound phosphine with carbon tetrachloride and tiiethylamine has also been reported. ... 

Preparative applications of these reactions have included work on peptide synthesis from amino-acids (suitably protected) using triphenyl phosphine (120)10 7 >108 or a polymer-bound aryldiphenylphosphine (128).109 Coupling is generally very efficient,107 but racemization problems occur in some reactions.108 109 A typical coupling reaction using (128) is outlined in Scheme 9. 

A library of 63 peptides, each containing one of the two phosphine-substituted amino acids 8 or 9, was prepared by Gilbertson and coworkers in a parallel synthesis on polymer beads [13]. After complexation of all peptides with rhodium, the obtained polymer-bound complexes were employed in the asymmetric hydrogenation of 10 (Fig. 5). 

Allylic substitution reaction cyclopentenyl acetate plus dimethylmalonate 136 Phosphines bound to /3-turn peptides linked to a solid support Pd Array of vials, 2 ml, RT NMR Pd catalyst identified, ee values up to 95% 2004 117a... 

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