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.

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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].

A new triterpene cycloartane glycoside called askendoside K was isolated from roots of Astragalus taschkendicus Bunge (Leguminosae). The structure of this glycoside was established using chemical and biochemical transformations and spectral data.In continuation of research on polar triterpene glycosides from Astragalus taschkendicus Bunge (Leguminosae) [1], we isolated one more new glycoside from roots of this plant and called it askendoside K (1). Herein we report the structure determination of this glycoside.The PMR spectrum of 1 (Table 1) exhibited at strong field 1H doublets for an AX system at G 0.06 and 0.35 that belonged to the isopropane methylene of a cyclopropane ring in addition to resonances for seven methyls. As expected, the 13 C NMR spectrum of this same glycoside showed resonances at G 21.12, 29.03, and 30.23 for quaternary C-9 and C-10 and methylene C-19 composing the three-membered ring, indicating that the studied glycoside was a cycloartane triterpenoid [2][3][4][5]. 1 2 -4, 6 5 OH OH OH OH O O HO OH OH O HO HO O OH OH O CH 2 OH OH O CH 3 OOC 2 -5 6 Enzyme Í + OH OH OH OH RO R 1 O OH OH OH OH O O HO O OH OH OH O O HO HO HO O OH OH O CH 2 OH OH O HOOC 2: R = R 1 = H; 3: R = E-D-Xylp, R 1 = H 4: R = H, R 1 = E-D-GlcUA(1o2)-E-D-Glcp 6: R = D-L-Arap(1o2)-E-D-Xylp, R 1 = E-D-Glcp