High yielding selective access to spirocyclopropanated 5-oxopiperazine-2-carboxylates and 1,4-diazepane-2,5-diones from methyl 2-chloro-2-cyclopropylideneacetate
Facile synthesis of structurally diverse 5-oxopiperazine-2-carboxylates as dipeptide mimics and templates
作者:Michael Limbach、Alexander V. Lygin、Vadim S. Korotkov、Mazen Es-Sayed、Armin de Meijere
DOI:10.1039/b908548c
日期:——
A sequence of Michael addition of a primary amine onto methyl 2-chloro-2-cyclopropylidene-acetate (1), acylation of the adduct with α-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 α-bromophenylacetic acid chloride, the trans-configured 6-phenyl-5-oxopiperazine-2-carboxylates are formed preferentially.
High yielding selective access to spirocyclopropanated 5-oxopiperazine-2-carboxylates and 1,4-diazepane-2,5-diones from methyl 2-chloro-2-cyclopropylideneacetate
作者:Michael Limbach、Vadim S. Korotkov、Mazen Es-Sayed、Armin de Meijere
DOI:10.1039/b809174a
日期:——
The 2-spirocyclopropanated methyl 5-oxopiperazine-2-carboxylate 3 and the 3-spirocyclopropanated 6-chloro-1,4-diazepane-2,5-dione 4 could both be prepared at choice in 93 and 88% yield, respectively, from methyl 2-chloro-2-cyclopropylideneacetate (1) in a sequence of Michael addition of 3-benzyloxypropylamine, peptide coupling with N-Boc-glycine, Boc-group removal and cyclization. Transformation of the benzyloxypropyl side chain, peptide coupling with N-Boc-(S)-asparagine, deprotection and repeated cyclization led to the octahydro[2H]pyrazino[1,2-a]pyrazinetrione scaffold 10 containing a rigidified mimic of a tripeptide with a DGR motif. The overall yield of 11 after deprotection of 10 (a total of 13 steps in 8 distinct operations) was 30%.