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2004
Peptides
U 0400
45- 201
Asymmetric Nucleophilic Substitution of α-Bromo Amides via Dynamic Kinetic
Resolution for the Preparation of Dipeptide Analogues. — Asymmetric nucleophilic substitutions of the title compounds (I) or (IV) in the presence of Bu4NI/NEt3
give the dipeptide analogues (III) and (V) with up to 99% diastereoselectivity. A small
enhancement of diastereoselectivity is observed by the use of Et-N(iPr)2 as the base.
Mechanistic investigations suggest that α-bromo acetamides are configurationally labile under the reaction conditions and the primary step of the asymmetric induction is
a dynamic kinetic resolution. Functionalization of the amine by standard procedures
(e.g. deprotection with cyclohexadiene/Pd-C) offers a simple route to D-arylglycine
dipeptides. — (NAM, J.; CHANG, J.-Y.; SHIN, E.-K.; KIM, H. J.; KIM, Y.; JANG, S.;
PARK*, Y. S.; Tetrahedron 60 (2004) 30, 6311-6318; Dep. Chem., Kon-Kuk Univ.,
Kwangjinku, Seoul 143-701, S. Korea; Eng.) — Kieslich
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