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Synthesis of N-glycoconjugates of glycyrrhetic acid

“…The triterpene parts of the 13 C NMR spectra of 2, 3, and 6 were identical to those of the starting 3-O-acylates [4]. Signals in the 13 C NMR spectra of newly synthesized N-glycoconjugates were assigned based on literature data for glycyrrhetic acid derivatives [4,5] and starting β-glycosylamines [6][7][8]. The CSs of C8 and C14 were defined more accurately using our published 1 H and 13 C high-resolution spectra (600 and 125 MHz) for glycyrrhizic acid and its derivatives [9].…”

“…The triterpene components were glycyrrhetic acid methyl ester 3-O-hemisuccinate and -phthalate, which were prepared previously [4]. These were condensed with the glycosylamines using N,N′-dicyclohexylcarbodiimide (DCC) in dimethylformamide (DMF):pyridine (Py).…”

“…The low yield (49%) of 3 was explained by losses during chromatography and formation of N-acylurea as a side product [5]. The starting material methylglycyrrhetate 3-O-hemisuccinate was isolated as an impurity (30%) during chromatography and identified by TLC and 13 C NMR spectroscopy [4]. The yield of N-glycoconjugate 5 was higher (62%) if methylglycyrrhetate acid phthalate was acylated with β-D-lactosylamine using DCC in the presence of a nucleophile, N-hydroxybenzotriazole (HOBt).…”

“…The PMR spectrum of peracetate 4 showed seven acetyls in the range 2.0-2.1 ppm, the succinic CH 2 at 2.3 ppm, and the NH proton at 7.2 ppm. The triterpene parts of the 13 C NMR spectra of 2, 3, and 6 were identical to those of the starting 3-O-acylates [4]. Signals in the 13 C NMR spectra of newly synthesized N-glycoconjugates were assigned based on literature data for glycyrrhetic acid derivatives [4,5] and starting β-glycosylamines [6][7][8].…”

Glycyrrhizin and glycyrrhetic acid: scaffolds to promising new pharmacologically active compounds

“…Starting from penta-acetyl GL (63) or penta-acetyl GL 30-methyl ester (64), Kondratenko et al 13 synthesized new saponin compounds with monossacharide residues of glucose and galactose through ester bonds (65-69, Scheme 6). Compound 69, in the model of experimental rat stomach lesions induced by acetylsalicylic acid, expressed anti-ulcer effects at the dose of 25 mg kg -1 (orally administered), against 100 mg kg -1 of the standard drug carbenxolone or 50 mg kg -1 of GL.…”