13C NMR spectra of a number of penta- and hexacyclic triterpenoids derived from glycyrrhetic acid

The¹³C NMR spectra of 22 derivatives of 18α- and 18β-glycyrrhetic acids that have been investigated and an assignment of the signals has been made. It has been shown that a modification of the carboxy group of glycyrrhetic acid leads mainly to a change in the chemical shifts of the α-, β-, and γ-carbon atoms of ring E. The assignment of a number of signals has been confirmed by the use of the shift reagent Eu(fod)_s. It has been established that the C₂₈ and C₁₆ signals are the most sensitive to a change in the C₁₈ configuration in the spectra of glycyrrhetic acid derivatives.

     

Synthesis of 4,5-Seco-Derivatives of Allobetulin

4,5-Seco-19,28-epoxy-18-olean-3,5-dione wasprepared by ozonation of 19,28-epoxy-18-olean-3(5)-ene. The structures of the synthesized compounds were confirmed using spectral data.     

Synthesis of Triterpene Derivatives of D-Glucosamine - Modified Analogs of Glycyrrhizic Acid

Triterpene D-glucosamine amides containing 18α- and 18β-glycyrrhetic acid succinates were synthesized.__________Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 7–9, January–February, 2005.     

Stereoselective synthesis of triterpene 2-deoxy-α-d-lyxo-hexopyranosides

2-Deoxy-α-d-lyxo-hexopyranosides of 18β-glycyrrhetic acid, its 11-deoxo derivative and allobetulin were synthesized by glycosylation of oleonane-type triterpene alcohols withd-galactal acetate in the presence ofN-iodosuccinimide followed by deiodination and deprotection. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 596–600. March, 1997.     

Interaction of singlet oxygen with biomolecules, 2.1O2 quenching by glycirrhizic acid derivatives

Overall constants for the singlet oxygen quenching rate by β-glycirrhizic acid derivatives (ether, amide, isocyanate, isothiocyanate, urethane, glycopeptide) are determined. Introduction of substituents in the β-glycirrhizic acid molecule decreases the rate constant by 1–3 orders of magnitude. Part 1:Bull. Russ. Acad. Sci., Div. Chem. Sci.,46, 49 (1996)     

Synthesis and anti-HIV activity of triterpene 3-<Emphasis Type="Italic">O</Emphasis>-galactopyranosides,analogs of glycyrrhizic acid

A new method for synthesizing triterpene 3-O-galactosides, analogs of glycyrrhizic acid (GA) based on 18βglycyrrhetic acid (GLA) methyl esters and 18,19-dehydro-GLA, using 2,3,4,6-tetra-O-acetyl-a-Dgalactopyranosyl bromide as the glycosyl donor, I–Br promoter, and 4-? molecular sieves was developed. The method could produce primarily 3-O-α-D- or β-D-galactopyranosides depending on the reaction conditions. The 3-O-α-D-galactopyranoside of GLA exhibited an index of selectivity (IS) 2.9 times greater than that of GA for inhibition of accumulation of virus-specific protein p24 of HIV-1. β-D-Galactopyranoside of GLA was more cytotoxic for MT-4 cells and exhibited weak anti-HIV-1 activity.     

Synthesis of Benzyl Esters of Glycyrrhizic Acid in the Presence of Phase-Transfer Catalysts

Benzyl esters of glycyrrhizic acid were synthesized using PhCH₂Br in DMSO-CH₂Cl₂-NaOH in the presence of phase-transfer catalysts, such as tetraalkylammonium salts and 2-methyl-2-propanol.     

Direct stereospecific synthesis of triterpene and steroid 2-deoxy-α-glycosides

Stereospecific synthesis of 2-deoxy-α-glycosides of methyl glycyrrhetate, methyl deoxycholate, and cholesterol was performed by glycosylation of the corresponding alcohols with glycal acetates in the presence of a cation-exchange resin (H⁺) and LiBr. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1390–1393, July, 1997.