From the adduct 8, obtained from naphthazarin (6) and the diene 7, the olefin 25 is synthesized via epoxidation ( 15) and treatment with base. Cleavage of the silyl ethers 25 yields the allylic alcohol 26 which can be epoxidized to give 28 and 30 and subsequently cleaved with methanol to yield the methyl ethers 32 and 33. The relative configuration of the acetonide 36 obtained from 33 is confirmed by X-ray analysis; consequently, the relative configuration 1 a of altersolanol A is proved. Furthermore, the mass spectrometrical investigations support the stereochemistry of the isomers 31- 33. The tetracyclic anthracyclinones 40- 42 are synthesized by Diels-Alder reaction of 31, 33, and 36 with 1-methoxy-1, 3-butadiene.
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