title: Facile synthesis of structurally diverse 5-oxopiperazine-2-carboxylates as dipeptide mimics and templates.
abstract: A sequence of Michael addition of a primary amine onto methyl 2-chloro-2-cyclopropylidene-acetate (1), acylation of the adduct with alpha-bromo acid chlorides under modified Schotten-Baumann conditions and ring-closing twofold nucleophilic substitution on the thus formed bishalides 3a-e with aliphatic or aromatic amines according to a very simple protocol with final acid/base extraction or filtration over silica gel for purification leads to the 3-spirocyclopropanated 5-oxopiperazine-2-carboxylates 2 or in two cases, after intermolecular transesterification of 2, to bicyclic oxopiperazines 6, with a remarkable variability of the substituents R1-R3 in 39-99% yields (20 examples). Starting with alpha-bromophenylacetic acid chloride, the trans-configured 6-phenyl-5-oxopiperazine-2-carboxylates are formed preferentially.
authors.affiliation: Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Limbach
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Lygin
authors.forename: Vadim S
authors.initials: VS
authors.lastname: Korotkov
authors.forename: Mazen
authors.initials: M
authors.lastname: Es-Sayed
authors.forename: Armin
authors.initials: A
authors.lastname: de Meijere
mesh_terms: D000588:Amines / Q000737:chemistry; D032701:Biomimetics / Q000379:methods; D002264:Carboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D004151:Dipeptides / Q000138:chemical synthesis*; D018716:Molecular Mimicry / Q000502:physiology*; D013237:Stereoisomerism
chemical_list: D000588:Amines; D002264:Carboxylic Acids; D004151:Dipeptides