Oleanenes

Sometimes several of these rearrangements occur in one molecule, either simultaneously or in rapid succession. A spectacular example is found in the triterpene series. Friedelin is a triterpenoid ketone found in cork. Reduction gives 3p-friedelanol (47). When this compound is treated with acid, 13(18)-oleanene (48) is formed. In this case seven 1,2 shifts take place. On removal of H2O from position 3 to leave a positive charge, the following shifts occur hydride from 4 to 3 methyl... 

The alcohol 3) , 28-diacetoxy-6 -hydroxy-18i -12-oleanene was oxidised in an aqueous acetic acid medium Deuteration at the six position had no effect on the rate in solvents of high (> 80 %) acetic acid content, but the isotope effect reached 2 in 60 % acetic acid. Increasing the acetic acid content of the medium produced a much larger effect on the oxidation rate of cyclohexanol than of the polycyclic alcohol. 

Fujikawa et al. made the interesting observation that an extract from the stem bark given orally at a dose of 250 mg/kg once a day for 2 weeks protects rats against MPTP-induced Parkinsonian bradykinesia and catalepsy and inhibited neuronal loss of dopamine (70). The active constituents involved here are unknown. Note that the plant abounds with pentacyclic oleanene saponins (71-73). Note that Acanthopanax species are known to elaborate a series of diterpenes, a group that has the potency to bind to dopamine receptors, as reported in Vitex agnus-castus. Are diterpenes involved in the dopaminergic properties of Acanthopanax gracilistylus W. W. Sm. ... 

Masazumi M, Yoshiteru I, Susumu I, Junzo S. Epi-Oleanene type triterpene glycosyl esters from leaves of Acanthopanax spinosus. Phytochemistry 1993 33 891-895. 

Under more vigorous conditions (0.2-0.5 eq. of the catalyst), the dehydration of the 3 (3-hydroxyl group occurred and the resulting compounds underwent a double Wagner-Meerwein rearrangement, originating A-neo-18a-oleanene compounds in high yields (Scheme 40). 

Murakami and M. Yoshikawa. Structures of new acylated oleanene-type triterpene oligoglycosides, teasaponins E-I and E-2, from the seeds of tea plant. Camellia sinensis (L.) O. Kuntze. Chem Pharm Bull 1998 46(12) 1901-1906. 

Cui, B., Y. Sakai, T. Takeshita, J. Kinjo, and T. Nohara. 1992. Four new oleanene derviatives from the seeds of Astragalus complanatus. Chem. Pharm. Bull. 40 136-138. 

BIOACTIVE OLEANENE GLUCURONIDES OBTAINED FROM FABACEOUS PLANTS... 

Table 1. Characteristic Oleanene Glucuronides (OGs) Isolated from... 

Table 2. Hepatoprotective Activity of Some Oleanene Giucuronides and...

Fig. (14). Structure-Antiherpetic Activity Relationships of Oleanene Glucuronides...

Various other oleanene glucuronides having a characteristic functional group were also tested and the structure-anti-complementary activity... 

Sometimes, several rearrangements occur consecutively. A spectacular case has been observed (76-79) in the acid-catalyzed transformation of 3-a-fried-elanol (221) into 13(18)-oleanene (222). In this case, 221 gave presumably the carbonium ion 223 which underwent six stereoelectronically controlled... 

The photochemical reaction of 16-oxo-oleanenes, e.g. (106), results in the formation of only y-hydrogen transfer products, e.g. (107). A similar type... 

Cyclic Dihydroxy Compounds. Pentacyclic triterpenes in olive oil include 3p,17p-dihydroxy-12-oleanene (erythrodiol) and its parent compound uvaol, obtained largely from the epicarp and therefore characteristic of solvent extracted oils (42, 65). 

Triterpenic Acids. The following pentacyclic mono- and dihydroxy triterpenic acids are present in virgin olive oil (35, 43, 44) 3p-hydroxy-17-carboxy-5-12-olea-nene (oleanolic acid) 3 3,2a-dihydroxy-17-carboxy-5-12-oleanene (maslinic acid) 3p-hydroxy-17-carboxy-8-12-ursene (ursolic acid) 2a,3p-dihydroxy-17-carboxy-5-12-ursene (2a-hydroxyursolic acid) and deoxyursolic acid (structure not fully elucidated). 

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