The structure of a new triterpenoid, secomacrogenin B, which was isolated from Astragalus macropus Bunge (Leguminosae) roots and is 24R-9,10-seco-cycloartan-1(10),9(11)-dien-3E,7E,24,25-tetraol, was elucidated. In continuation of structural investigations of triterpenoids from Astragalus macropus Bunge (Leguminosae), we showed that the chromatographically homogeneous compound C [1] was not a pure compound. Rechromatography of this mixture over a column produced two fractions. The first contained a mixture of compounds. The second was a pure compound. Herein we present data on the structure elucidation of the latter, which we called secomacrogenin B (1).The molecular formula of the new compound 1, C 30 H 50 O 4 , which was derived from NMR spectral data [1] and confirmed by quasi-molecular ions in positive-and negative-ion electrospray mass spectra (ESI-MS and ESI-MS), indicated that it was triterpenoid in nature. An examination of PMR and 13 C NMR spectra confirmed this conclusion ( Table 1) and indicated that all O atoms were hydroxyls, three of which were secondary and one of which was tertiary. Therefore, 1 had six degrees of unsaturation. Because 1 contained two double bonds, it should have consisted of four rings, which is one ring less than for cycloartane triterpenoids. The PMR and 13 C NMR spectra indicated that the cyclopropane ring was missing and that seven methyls were present. Therefore, 1 was not a lanostane or cucurbitane triterpenoid, which are biologically related to cycloartanes [2]. In other words, 1 retained the 9,19-and 10,19-bonds. That meant that the 9,10-bond had been lost and, therefore, the new triterpenoid 1 was a 9,10-seco-cycloartane triterpenoid.The PMR spectrum of 1 showed 1H doublets for an AX system of an isolated methylene at G 2.77 and 3.03. The doublet at G 2.77 in the HMBC spectrum had cross-peaks with four olefinic C atoms (G 139.49, 135.82, 126.23, 117.17) and two methine C atoms that resonated at G 44.99 and 55.74.Because the last resonances belonged to C-5 and C-8, respectively, the isolated methylene was CH 2 -19. Therefore, the double bonds were located on C-1-C-10 and C-9-C-11 and 1 had a 9,10-seco-cycloart-1(10),9(11)-diene C skeleton.The same PMR spectrum showed only one methyl group as a doublet. This defined the location of the tertiary hydroxyl as C-25.

In continuation of research on cycloartane triterpenoids from plants of the genus Astragalus (Leguminosae) [1], we determined the structure of the new compound H [2], which was isolated from Astragalus macropus Bunge and which we called cyclomacroside D (1).PMR and 13 C NMR spectra of 1 (Table 1) indicated the presence of a 1,1,2,2-tetrasubstituted 9,19-three-membered ring (1H doublets for an AX system at δ 0.44 and 0.89 with SSCC 2 J = 4 Hz, C-9 and C-10 singlets, and C-19 triplet). This classified the studied glycoside as a triterpenoid of the cycloartane series [3][4][5][6].Comparison of the 13 C NMR spectra of 1 and the genin 3 showed that cyclomacroside D was a derivative of cyclomacrogenin B.Acid hydrolysis of cyclomacroside D and subsequent analysis of the carbohydrate part of the hydrolysate by paper chromatography detected D-xylose and L-rhamnose. The PMR and 13 C NMR spectra of 1 contained two sets of resonances for monosaccharide units. Therefore, 1 was a bioside containing D-xylose and L-rhamose in a 1:1 ratio.As expected, the native genin cyclomacrogenin B could not be detected in the genin part of the acid hydrolysate of the glycoside. The presence of the 1α-hydroxyl, which is easily eliminated in acidic medium, caused migration of the 9,19-bond to a 1,19-bond and generated a 9(11) double bond [3].Enzymatic hydrolysis of cyclomacroside D by gastric juice of the grapevine snail (Helix pomatia) formed progenin 2, which was identified as cyclomacroside C [1]. This indicated that the L-rhamnose was bonded to the genin at C-3 of the α-glycoside bond and that the monosaccharide has the 1 C 4 -conformation. In agreement with this, the HMBC spectrum contained a cross-peak between resonances for the anomeric H atom of the α-L-rhamnose unit and C-3 of the genin. The resonance for H-1 of D-xylose in the same HMBC spectrum correlated with the resonance of C-24, indicating the site of attachment of the pentose.In fact, C-3 and C-24 experienced a glycosylation effect and resonated at δ 84.19 and 89.56. Chemical shifts of H and C atoms and SSCC of D-xylose in the PMR and 13 C NMR spectra of 1 indicated the pyranose form, the 4 C 1 -conformation, and the β-configuration of the studied monosaccharide.Thus, cyclomacroside D has the structure 24R-cycloartan-1α,3β,7β,24,25-pentaol 3-O-α-L-rhamnopyranoside-24-O-β-D-xylopyranoside.

In continuation of the chemical transformation of cycloartane triterpenoids [1], we synthesized partially cycloasalgenin (6), which was isolated from Astragalus zahlbruckneri Hand.-Mazz. (Leguminosae) in Turkey [2] and described without naming. For convenience, we called it cycloasalgenin. Cycloasalgenin is a 16-keto derivative of cyclosiversigenin. Therefore, we synthesized cycloasalgenin in three steps starting from cyclosiversigenin (1).Cyclosiversigenin was acetylated by acetic anhydride in Py. The 3,6-diacetate (2), 6-monoacetate (3), and 3-monoacetate (4) of cyclosiversigenin, which were previously described [3,4], were isolated from the reaction products.Jones oxidation [5] was used to introduce the C-16 ketone into 2. This produced 5, the PMR spectrum of which exhibited at strong field (G 0.80-1.19) resonances for seven methyls. This indicated that the side chain was retained. The resonance of H-17 in this same spectrum became a singlet at G 2.85. This was consistent with oxidation of the 16E-hydroxyl into a ketone. This was also consistent with the 13 C NMR spectrum of 5, where the C-16 resonance appeared at G 218.08.The protecting groups were removed by alkaline hydrolysis of the diacetate of 5. Ketones 6 and 7 were isolated from the hydrolysis products.The PMR and 13 C NMR spectral data of 6 enabled it to be identified as cycloasalgenin [2]. A compound with an identical structure was obtained during elucidation of the structure of cycloastragenol (cyclosiversigenin) [6].

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In continuation of research on triterpene glycosides in plants of the genus Astragalus (Leguminosae), we studied A. sieversianus Pall. growing in the Republic of Kyrgyzstan [1] and indigenous to the Republic of Uzbekistan and the People's Republic of China. The chemistry of this species is well studied [2-10]. We isolated 16 cyclosieversigenin glycosides from this plant [11].Total triterpene glycosides from roots of A. sieversianus, called astragaloside, possess hypocholesterolemic activity, enhance lipid metabolism, and improve cardiac activity of test animals with experimental endogenous hypercholesterolemia [12]. The extract of this plant exhibits diuretic and hypotensive activity and prevents the appearance of experimental stomach ulcer [13]. Cyclosieversioside D (7) and other analogs of cyclosieversioside F (4) exhibit antiviral and antitumor activity and low toxicity in oral and parenteral administration. The studied glycosides are interferon inductors [14]. 1: R = R 1 = Ac, R 2 = H, R 3 = β-D-Xylp; 2: R = R 1 = Ac, R 2 = H, R 3 = β-D-Glcp 3: R = α-L-Rhap, R 1 = Ac, R 2 = H, R 3 = β-D-Xylp; 4: R = R 1 = R 2 = H, R 3 = β-D-Glcp 5: R = α-L-Rhap, R 1 = R 2 = H, R 3 = β-D-Xylp; 6: R = α-L-Rhap, R 1 = R 2 = H, R 3 = β-D-Glcp 7: R = H; 8: R = β-D-Glcp