Synthesis of Angucyclines. 8. Biomimetic-Type Synthesis of Rabelomycin, Tetrangomycin, and Related Ring B Aromatic Angucyclinones.
The angucyclinones with aromatic ring B (1a-c and 2a-c) are prepared in a biomimetic-type synthesis by two successive aldol cyclizations starting from the substituted naphthoquinones 12a-c. In both cyclization steps the C-H acidity of the potential nucleophilic centers determines the mode of cyclization under kinetically controlled conditions. The tetrahydroanthraquinones 13a-c/14a-c are hydroxylated at C-4 to the phenolic anthraquinones 16a-c upon treatment with excess NMO.
Krohn
Karsten
K
Universität-GH-Paderborn, FB Chemie und Chemietechnik, Warburger Str. 100, 33098 Paderborn, Germany.
Böker
Norbert
N
Flörke
Ulrich
U
Freund
Christian
C