An efficient chemical method for separation of corsolic acid from its isomeric maslinic acid

Abstract

Based on the difference in steric bulk around C12-C13 double bond, the two isomeric dihydroxy pentacyclic triterpenic acids viz: corsolic acid and maslinic acid have been quantitatively separated via their methyl esters by reacting with the bulky m-chloroperbenzoic acid. Corsolic acid methyl ester was obtained in pure form, whereas maslinic acid methyl ester was separated as 12-oxo derivative formed via its epoxide. Alkaline hydrolysis of corsolic acid methyl ester afforded the desired acid. This method was also found to work well with the isomeric amyrin mixture (alpha- and beta-), but not highly selective. The high selectivity of this method with corsolic maslinic acid system can be rationalized in terms of 2alpha-hydroxy functionality, which provides additional crowding around the double bond and completely prevented corsolic acid from its reaction with perbenzoic acid.

Oxidative lactonization of oleanane and ursane acids by treating with ozone

“…For example, the oxidation of methyl ursolate with ozone proceeds with generation of 12-oxo-11S,13R-oxetane fragment in the cycle С [21], whereas the oxidation of methyl oleanate leads to methyl 12-oxooleane [22]. Different courses of oxidation processes of triterpenoids belonging to the α-and β-amirine series with reagents like m-chloroperoxybenzoic acid and HCOOH-H 2 O 2 underlie their separation in the form of oxyderivatives, because in plants these metabolites often accompany each other [3,23,24].In continuation of our research on the oxidative transformations of vegetable terpenoids [25][26][27][28][29][30][31] we investigated in the present study the oxidation of С 12 =С 13 bond of the ring С in oleanane and ursane acids with ozone involving the free carboxy group (oxidative lactonization).Oxidative lactonization of oleanolic acid at the treatment with ozone was investigated before in various solvents (ethyl acetate, N,N-dimethylacetamide-MeOH, СН 2 Сl 2 -MeOH) with generation of three types of structures: 12α,13α-epoxides, 12α-hydroxy- …”

“…For example, the oxidation of methyl ursolate with ozone proceeds with generation of 12-oxo-11S,13R-oxetane fragment in the cycle С [21], whereas the oxidation of methyl oleanate leads to methyl 12-oxooleane [22]. Different courses of oxidation processes of triterpenoids belonging to the α-and β-amirine series with reagents like m-chloroperoxybenzoic acid and HCOOH-H 2 O 2 underlie their separation in the form of oxyderivatives, because in plants these metabolites often accompany each other [3,23,24].…”