Stereocontrolled construction of conformationally constrained and rigid bis(a-amino acid) derivatives
K. Undheim, J. Efskind, and G. B. Hoven
Department of Chemistry, University of Oslo, N-0315
Oslo, Norway
Abstract: Cystine is regarded as a four-atom bridged
bis(a-amino acid). The bridge between the
two glycine moieties in cystine has been replaced with all-carbon C4-bridges
between the a-carbon of the glycines. The
products are dicarba analogs of cystine. Conformational constraints
have been conferred on these molecules by insertion of cis-
and trans- double bonds in the bridge, by alkylidene substituents,
by insertion of a triple bond, by insertion of aromatic or heteroaromatic
rings, or otherwise by ring formation. Particularly rigidified dicarba
analogs of cystine have been prepared where the a-amino
acid carbon is quaternary and part of tricyclic ring structures. Ru(II)-catalyzed
ring-closing metathesis (RCM) reactions have been widely used in the
preparation of cyclic amino acids. Conformational constraints in acyclic
structures result from substitution by simple alkyl, alkenyl, or alkynyl
groups at the a-amino acid carbon in the
formation of a-quaternary amino acid derivatives.
*Pure Appl.Chem. 75,
141�419 (2003). An issue of reviews and research papers based on
lectures presented at the 23rd IUPAC International Symposium on the
Chemistry of Natural Products, Florence, Italy, 28 July � 2 August 2002.
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