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Chiral in peptide synthesis

Conversion of the carboxyl group to a more reactive group and coupling are key steps in peptide synthesis. The coupling reaction must occur readily and quantitatively, and with a minimum of racemization of the chiral centers in the molecule. This last criterion is the Achilles heel of many possible coupling sequences. The importance of nonracemization can best be appreciated by an example. Consider synthesis of a tripeptide from three protected... [Pg.1238]

The 4.4,4-trifluoro-3-oxobut-l-enyl group has been proposed as a suitable group for the protection of the N —H terminal of amino acids in peptide synthesis. Chiral amino acids react with 4-etnoxy-1,l,l-trifluorobut-3-en-2-one (59) to give the N-prolected amino acids (e.g., 60) in good yields and with retention of chirality. The protecting group can be removed by acidic... [Pg.639]

Racemization of chiral centers during the isolation or synthesis of a particular peptide will lead to diastereoisomeric mixtures. In addition, in peptide synthesis it is often more efficient to use DL-amino acids, particularly if they are specifically labeled with C, H, S, etc. Rapid... [Pg.126]

Active esters are chirally stable under the usual conditions of coupling in peptide synthesis, but with the single exception of piperidino esters they may undergo isomerization if left in the presence of tertiary amines. In addition to their role as shelf-stable reagents, active esters are postulated as intermediates in carbodiimide-mediated reactions where a substituted hydroxylanoine is added in order to suppress the side reaction of epimerization in the... [Pg.444]

Unfortunately, the 3-phenyl-2-thiohydantoins formed in the Edman stepwise degradation suffer racemisation (Davies and Mohammed, 1984) so that the method cannot be used to determine the configuration of amino acids in a peptide. This is not usually a serious limitation, but enantiomerisation is a perpetual hazard in peptide synthesis (Chapter 7). It is therefore desirable to determine if enantiomerisation has occurred at any residue. Such information could be important, for example, in dating bone proteins obtained in archaeological excavations. Examination of the chiral purity of the amino acids in a total acid hydrolysate is not satisfactory. [Pg.103]

Condensation of L-cysteine with carbonyl compounds has been widely employed in the preparation of chiral thiazolidine 4-carboxylic acids <87JMC1891>. a-Hydroxyketenes <87JHC1629> or sugar-derived aldehydes <89CAR(187)223> have been used to form 2-(polyhydroxyalkyl)thiazohdines (Equation (73)) <94CAR(262)147>. This reaction has been also employed in peptide synthesis <94JA4149>. [Pg.448]

Recently, Ellman expanded the scope to include N-tert-butyl imino esters 60 (Scheme 8.16) [42]. The resulting arylglycines 61, which are unnatural amino acids, are interesting chiral building blocks that might find application in peptide synthesis. [Pg.280]

Of the 20 amino acids that are commonly found in proteins, with the exception of glycine, all have a chiral centre of L-configuration at their a-carbon atoms, and two, isoleucine and threonine, also have a chiral centre in their side-chains. The biological properties of proteins and peptides are critically dependent on the configuration of the backbone chiral centres, so maintaining the integrity of these centres is of paramount importance in peptide synthesis. [Pg.31]

Related procedures have been used to generate a series of chiral aminoazirines derived from amino acids. These azirines have then been used as reagents in peptide synthesis. " An example is provided by the synthesis of a homoproline-derived azirine 5 (Scheme 6.3). ... [Pg.168]

A major trend in organic synthesis, however, is the move towards complex systems. It may happen that one needs to combine a steroid and a sugar molecule, a porphyrin and a carotenoid, a penicillin and a peptide. Also the specialists in a field have developed reactions and concepts that may, with or without modifications, be applied in other fields. If one needs to protect an amino group in a steroid, it is advisable not only to search the steroid literature but also to look into publications on peptide synthesis. In the synthesis of corrin chromophores with chiral centres, special knowledge of steroid, porphyrin, and alkaloid chemistry has been very helpful (R.B. Woodward, 1967 A. Eschenmoser, 1970). [Pg.215]


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See also in sourсe #XX -- [ Pg.208 ]

See also in sourсe #XX -- [ Pg.208 ]




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Chiral synthesis

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