Author:
Vydrina Valentina Afanasievna,Yakovleva Marina Petrovna,Kravchenko Aleksey Aleksandrovich,Sayakhov Rasul' Rustemovich,Ishmuratov Gumer Yusupovich
Abstract
The hydroboration-oxidation reaction is widely used in the chemistry of terpenoids both for proving the structure of new compounds isolated from natural raw materials and for the directed synthesis of low molecular weight bioregulators. Moreover, most of the known examples affect mono- and sesquiterpenes, a much smaller number - for di- and triterpenoids: most are represented by hydroboration-oxidation of localized double bonds, examples for conjugated dienes are limited only by hydroboration-oxidation of cis-eudesma-6,11-diene, abietic acid and its methyl ester.
We found that the reduction of the pentacyclic triterpenoid – glycyrrhetate methyl ester – diisobutylaluminium hydride in methylene chloride at -78 ° С and subsequent hydrolysis in the presence of ammonium chloride proceeds with the formation of 3β,30-dihydroxy-18βH-olean-9(11),12(13)-diene with a yield of 90%. It was shown that the hydroboration of the 1,3-diene system in it with a 3.3 molar excess of diborane in tetrahydrofuran is accompanied by the restoration of the carboxyl function, and after oxidation with the hydrogen peroxide-sodium acetate system of the organoboranes formed, three alcohols are mixed (2 : 1 : 1): 3β,11,30-trihydroxy-18βH-olean-12(13)-ene, 3β,12,30-trihydroxy-18βH-olean-9(11)-ene and 3β,9,30-trihydroxy-18βH-olean-12 (13)-ene, respectively. A similar mixture of triols was also obtained by hydroboration-oxidation of 3β-hydroxy-18βH-olean-9(11),12(13)-diene-30-oic acid. The hydroboration-oxidation reactions of 3β,30-dihydroxy-18βH-olean-9(11),12(13)-diene or the corresponding 30th acid proceed as monoprocesses predominantly at 9(11) double bonds.
Subject
Organic Chemistry,Plant Science,Biomaterials
Reference26 articles.
1. Mikhaylov B.M., Bubnov Yu.N. Bororganicheskiye soyedineniya v organicheskom sinteze. [Organoboron compounds in organic synthesis]. Moscow, 1977, 516 p. (in Russ.).
2. Brown H.C., Krishnamurthy S. Tetrahedro, 1979, vol. 35, no. 5, pp. 567–607. DOI: 10.1016/0040-4020(79)87003-9.
3. Brown H.C., Ramachandran P.V. Reduction in organic synthesis. Washington, DC, 1996, pp 1–30.
4. Plemenkov V.V. Vvedeniye v khimiyu prirodnykh soyedineniy. [Introduction to the chemistry of natural compounds]. Kazan, 2001, 376 p. (in Russ.).
5. Brown H.C., Brown H.C., Suzuki A. J. Am. Chem. Soc., 1967, vol. 89, no. 8, pp. 1933–1941. DOI: 10.1021/ja00984a031.