Total synthesis of dehydroaltenuene A. Revision of the structure and total synthesis of dihydroaltenuene B.
Total synthesis of alternaria toxins starting from previously synthesized altenuene (3) and isoaltenuene (4) is described. Dihydroaltenuene B (9) was prepared by hydrogenation of 3, and the non-natural epimer 3-epi-dihydroaltenuene A was obtained analogously from 4. Inspection of the spectroscopic data for 9 revealed that the originally proposed structure was in error. A revised structure (11), unambiguously proven by total synthesis, is reported herein. Oxidation of 4 with oxygen in the presence of palladium(II) acetate as catalyst led to the formation of dehydroaltenuene A (8), while oxidation of 3 using identical conditions yielded ent-dehydroaltenuene B (ent-9). Oxidation of 4 with manganese(IV) oxide furnished dehydroaltenusin (12), although only impure material was obtained in low yield.
Altemöller
Martina
M
Institut fur Organische Chemie, Universitat Karlsruhe, Karlsruher Institut fur Technologie, Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany.
Podlech
Joachim
J
D000528:Alternaria / Q000737:chemistry; D002384:Catalysis; D006865:Hydrogenation; D007783:Lactones / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry; D013237:Stereoisomerism
D007783:Lactones; C543756:dehydroaltenuene A; C543757:dihydroaltenuene B; C040005:altenuene; D010165:Palladium