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Abstract: (Chemical Abstract 2003, 139: 101292)
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Several triterpenic derivatives, with the A-ring functionalized, were semi-synthetized
from oleanolic and maslinic acids. The reactivities of sulfites, sulfate and epoxides
in these triterpene compounds were investigated under different reaction conditions.
Moreover, contracted A-ring triterpenes (five-membered rings) were obtained, by different
treatments of the sulfate (7). From the epoxide (8), deoxygenated and halohydrins derivatives
were semi-synthetized with several nucleophiles. Ozonolysis and Beckmann reactions were used
to yield 4-aza compounds, from five-membered ring olanediene triterpenes.
X-ray structure of sulfate (7) was given and compared with DFT geometries.
Theoretical 13C and 1H chemical shifts (GIAO method at the B3LYP/6-31G*//B3LYP/6-31G* level)
and 3JH,H coupling constants were calculated for compounds 5-9 and 34-36, identifying the
(R or S)-sulfur and (a or ß)-epoxide configurations together with 4-aza or 3-aza structures.
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