X-ray crystallographic
analysis shows that endiandric acid and a derived lactone have the respective
structures 2-(6'- phenyltetracyclo[5,4,2,03,13,010,12]trideca-4',8'-dien-11'-yl)acetic
acid and 12-phenyl-3-oxapentacyclo[7,5,2,02,6,07,15,013,16]hexadecan-4-one.
The structure (5) is proposed for the title compound
on the basis of chemical and spectroscopic evidence and on the X-ray crystal
structure of the derivative 4-{(Y-methyl-1'',3''-dioxo-7''-phenyl-
1'',3'',3'',4'',7'',7a''-hexahydroisoindol-4''-yl)methyl}tetracyclo [5,4,0,02,5,O3,9] undec-10-ene-8-carboxylic acid (9c).
For certain aromatic
nuclei, bromination in acetic acid and in the
presence of pyridine is accompanied by nuclear acetoxylation.
As first observed with galbulin, when two alkoxyl groups, one meta and one para to a benzylic centre of the substrate are present, acetoxylation occurs at the intervening ortho position. Under the given
conditions, acetoxylation occurs at position 8 of
6,7-dimethoxy-1-phenyl-1,2,3,4,-tetrahydronaphthalene, and at position 2 of
3,4,-dimethoxy diphenyl- and triphenyl-methanes. Acetoxylation does not occur in the absence of either of
the alkoxy groups or in the absence of pyridine, nor
does it occur in the pendant ring of 1-(3�,4�-dimethoxypheny1)-
1,2,3,4-tetrahydronaphthalene. These results are consistent with the earlier
suggestion that the reaction occurs by way of initial oxidative formation of a
doubly benzylic cation.
Wie schon im Falle von Galbulin (Ia) beobachtet, wird bei der Bromierung in Eisessig in Gegenwart von Pyridin außer dem Bromierungsprodukt (Ib) auch das Acetoxylierungsprodukt (Ic) gefunden.
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