Michael addition of the sodium enolate of a tert-butyl 0-keto ester to a 4,4,10-trisubstituted 8-formyl-A8-7-octalone (2)2 was shown earlier to afford adducts of general structure 3 which upon exposure to acid undergo tert-butyl ester cleavage, decarboxylation, and cyclodehydration to produce tricyclic enediones 6 or 8. Spectroscopic evidence, primarily NMR, is presented to demonstrate that the double bond in these enediones is normally in the 13,14 position (6) rather than the 8,14 position (8) when C-13 carries fewer than two substituents, and that the relative configuration of the carbon skeleton is trans-syn-cis in 6 and by inference trans-syn in 8. Intramolecular ketals 20 and 22, in which the C-10-C-9-C-8 configuration can only be anti-cis or syn-cis, were synthesized from enedione 6g by routes which do not alter the configuration at these sites. Relation of ketal 20 to saturated diketone 17, which must be either trans-anti-trans or trans-syn-cis because it does not epimerize in base, confirms the trans-syn-cis configuration of these substances. Stereoselectivity in the Michael addition producing adducts 3 therefore leads exclusively to the 9a orientation of the /5-keto ester side chain. In cases where more than one stereoisomeric adduct 3 is formed, it is shown that the configurational difference is only at C-ll.
Im Anschluß an frühere Untersuchungen wird die Reaktion des Decalons (I) zu den verschiedenen Kondensaten (VII) und (VIII) untersucht und deren Struktur über NMR‐Spektren sichergestellt.
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