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.