Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 1

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: electrophilic α-amination

Sortuj według:

Ogranicz wyniki do:

Asymetryczna synteza α,α-dipodstawionych α-aminokwasów

Kolesińska B.

Wiadomości Chemiczne

2010

[Z] 64, 7-8

673-728

In the last decade it has been observed rapid increas of application of noncoded α-amino acids as building blocks used for synthesis of analogues with improved and well defined advantageous properties. It has been found that the presence of α,α-disubstituted α-amino acid residues exhibit a pronounced helix-inducing potential which is responsible for a membrane destabilisation exerted by peptaibols [1]. Moreover, peptides containing α, α-disubstituted α-amino acid residues were found to exhibit enhanced resistance against chemical and enzymatic hydrolysis [2, 3], and acting as enzyme inhibitors, by mimicking ligand properties of their natural analogues, but preventing subsequent enzymatic reaction [6]. The increasing interest in the proprieties of α,α-disubstituted α-amino acids stimulates the search for new, effective methods of their synthesis. Among many methods of synthesis of α,α-disubstituted α-amino acids some can undeniably be regarded as classic approaches in asymmetric synthesis of α disubstituted α-amino acids such as the bislactim ether method proposed by Schöllkopf [25–35]. The others include the selfreproduction of stereogenic centre (the SRS method) discovered by Seebach [9–15] and developed by O'Donnel and the method of alkylation of benzofenone imine in the presence of chiral phase transfer catalysts [55, 56]. Depend on a character of bond which is created in asymmetric process all approaches to asymmetric synthesis of α,α-disubstituted α-amino acids can be divide into three categories. First of them is based on an introduction of alkyl substituents at the carbon atom. This approach can involve electrophilic alkylation of enolates, nucleophilic alkylation of C=N double bond, Mannich reaction etc. Second approach involves an introduction of α-amine group [70–78]. The last approach is based on an substitutionat α carbon atom of carboxylic function [82–95]. Another less general approaches consist of utilization of indirect methods including rearrangements or ring-opening reactions [100–112].