This chapter focuses on the isosteric replacement of peptide bonds with three different types of heterocyclic ring systems (1); @entity70047 (2), @entity70048 (3), and @entity41091 rings (4-6). The ring systems are similar in size and shape but show variations in aromatic, electrostatic, and @entity3884 bonding properties. These variations provide opportunities to study properties of importance for @entity6346 bond mimicry. The derivatives are synthesized from protected natural @entity1522 , and the reaction conditions have been chosen so that the enantiopurity is retained during the reaction sequences. Two series of mimetics will be described, one in which the @entity4880 functionality is directly attached to the heterocyclic ring (1) and one series with a @entity845 group inserted between the ring and the @entity4880 group (7). Since we have focused on the design and synthesis of @entity70049 mimetics, the synthetic examples described here start from L: - @entity815 . However, we have used the same synthetic scheme also for other @entity1522 and notes will be given when other derivatives require differences in reaction conditions (1). The use of the dipeptidomimetics as building blocks in pseudopeptide synthesis will also be described (7). These syntheses are performed on solid phase using Boc-chemistry. Also, the deprotection and purification of the pseudopeptides by reversed phase HPLC will be discussed.

Synthesis and Use of Pseudopeptides Derived from @entity70047 -, XXXX -, and @entity41091 -based Dipeptidomimetics.

@entity70047 :: ('CHEBI:46809', 'Chemical') :: ['1,2,4-oxadiazole'] @entity1522 :: ('CHEBI:33709', 'Chemical') :: ['amino acids'] @entity3884 :: ('MESH:D006859', 'Chemical') :: ['hydrogen'] @entity845 :: ('CHEBI:29358', 'Chemical') :: ['methylene'] @entity70049 :: ('MESH:C040500', 'Chemical') :: ['Phe-Gly'] @entity4880 :: ('CHEBI:33575', 'Chemical') :: ['carboxylic acid'] @entity815 :: ('CHEBI:28044', 'Chemical') :: ['phenylalanine'] @entity41091 :: ('MESH:C045575', 'Chemical') :: ['1,2,4-triazole'] @entity6346 :: ('CHEBI:32988', 'Chemical') :: ['amide'] @entity70048 :: ('CHEBI:46810', 'Chemical') :: ['1,3,4-oxadiazole']
@entity70048 :: (CHEBI:46810,Chemical) :: ['1,3,4-Oxadiazole']
