Oxidative radical cyclizations of diketopiperazines bearing an amidomalonate unit. Heterointermediate reaction sequences toward the asperparalines and stephacidins.
A novel approach to the diazabicyclo[2.2.2]octane core of prenylated bridged diketopiperazine alkaloids is described by direct oxidative cyclizations of functionalized diketopiperazines mediated by ferrocenium hexafluorophosphate or the Mn(OAc)3•2H2O/Cu(OTf)2system. Divergent reaction pathways take place depending on the substitution pattern of the substrates and the oxidation conditions such as temperature or the presence or absence of persistent radical TEMPO. For ester-substituted diketopiperazines, the ester group exerts a significant influence on the reaction outcome and stereochemistry of the radical cyclizations.
a Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo namesti 2 , Prague 6, Czech Republic.
Tynchtyk
T
Amatov
a Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo namesti 2 , Prague 6, Czech Republic.
Martin
M
Gebauer
a Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo namesti 2 , Prague 6, Czech Republic.
Radek
R
Pohl
b Department of Inorganic Chemistry, Faculty of Science , Charles University in Prague , Hlavova 2030/8 , Prague 2, Czech Republic.
Ivana
I
Cisařová
a Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo namesti 2 , Prague 6, Czech Republic.
Ullrich
U
Jahn
D000470:Alkaloids / Q000737:chemistry*; D003500:Cyclization; D054659:Diketopiperazines / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction
D000470:Alkaloids; D054659:Diketopiperazines
Alkaloids; diketopiperazines; oxidation; radical cyclizations; single electron transfer