Ph. D. THESIS 2009

Figure 9. ORTEP diagram for the bicyclic tetraester 1
In fact, the six-membered rings of the bicyclic skeleton are cyclohexene rings,
which adopt a flattened half-chair conformation.
Figure 10. X-ray structure for the bicyclic tetraester 1 displayed by Mercury program
The distances from the hydrogen atoms of OH groups to the carbonyl
O atoms are shown as a dashed line and are d = 1.851-1.860 Å. These low
values suggest strong interactions by hydrogen bonds and a high stability of the
cyclic structures.
The investigations of the molecular structure of compound 2 by single
crystal X-ray diffractometry indicated exclusively the presence of ketone form,
which contains two carbonyl groups located at the positions 3 and 3a of the
molecule (Figure 11).
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