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CARDIAC GLYCOSIDES FROM Strophanthus kombe I. F. Makarevich and S. V. KovalevUDC 547.92/93+615.224:547.918Twelve cardiac glycosides and aglycons were isolated from Strophanthus kombe seeds. Of these, eight were identified as

Twelve compounds including secologanin, loganin, the aglycon of loganin, and a new iridoid called glucologanin were isolated from fruit of common snowberry Symphoricarpos albus (L.) Blake. The structure of glucologanin was confirmed using PMR and mass spectroscopy and chemical transformations. 2′,3′,4′,6′,3′,4′, Common snowberry Symphoricarpos L. (Caprifoliaceae, honeysuckle) is a bush up to 1.5 m in height and is widely used as a decorative plant. In nature it is found mainly in North America and in the northern strip of European Russia. In Ukraine, white common snowberry Syphoricarpos albus (L.) Blake is most common.The phytochemistry of common snowberry is insufficiently studied. The contents in fruit of S. albus of phenolic acids [1], carbohydrates [2], and iridoids [3, 4] have been reported.We studied fruit of white common snowberry (S. albus) collected in October-November 2005 in the Botanical Garden of Karazin Kharkov National University (Ukraine). Fruit contains a large amount (85-87%) of water, which we took into account during its processing.Freshly collected berries were ground and extracted with n-butanol. The extract was divided into three fractions by polarity and chromatographed over columns using mixtures of CHCl 3 and CH 3 OH of increasing polarity for elution (see Experimental).A total of 12 pure compounds was isolated. Three of the isolated compounds were iridoids and were identified as secologanin (1), loganin (2), and loganigenin (3) [3, 5, 6]. A fourth glycoside (4) was new. The structures of 1, 2, and 3 were confirmed by PMR and mass spectrometry.Compound 1 was found to be highly unstable during its isolation. The compound was quickly oxidized in solutions by oxygen in air. The product of auto-oxidation was presumably cyclized to form lactone 8. The carboxyl and vinyl (ethylene) groups were involved in the cyclization. The product of auto-oxidation 8 was isolated during additional purification of 1 by column chromatography. Compound 8 contained two C=O groups according to IR spectra, one of which was an ester conjugated to a C=C bond (absorption band at 1696 cm −1 ); the second, a carbonyl of a seven-membered lactone ring (absorption band at 1655 cm −1 ).The PMR spectrum of 8 exhibited a characteristic resonance for the C-3 proton at 7.3 ppm, for the anomeric C-1′ proton at 4.5 ppm; a characteristic multiplet for the ester OCH 3 group at 3.7 ppm; and for protons H-5 and H-11 at 2.7 ppm. There was no resonance for an aldehyde.The mass spectrum of the lactone was consistent with the proposed structure of 8 (see Experimental). Compound 2 can exist as cyclic dimer 5. The C-7 OH group and ester carbonyl form two intermolecular H-bonds. The mass spectrum of the loganin dimer was consistent with the proposed structure of 5.

New aldimines were synthesized from the cardenolide strophantidin and cardenolide-glycosides erysimin and cymarin and included morpholine, nitrile, pyridine, furan, hydroxy-and methoxyphenyl, piperidine, and other derivatives. An effective modified method for synthesizing aldimines was proposed. 52 new compounds were synthesized. Their structures were confirmed by IR and PMR spectra and elemental analysis.We previously reported [1, 2] the synthesis of eight aldimines of strophantidin, some of which were slightly toxic cardiotonics, for example, adamantyliminostrophantidin [2].Therefore, it seemed advisable to continue research on the preparation of a broader set of new compounds with subsequent pharmacological screening. For this, we used amines of various structures.The starting natural compounds were the cardenolide strophantidin and the cardenolide-glycosides erysimin and cymarin, which have angular aldehydes [3]. These were synthesized by two methods. Organic compounds containing a free primary amine were reacted directly with the natural aldehydes by boiling in appropriate solvents and removing the water formed during the reaction by azeotropic distillation. It was found that the imines formed most rapidly and completely at the highest possible concentrations of the reactants, when the reaction mixture was like a melt. From the time such a state was reached, the reaction was finished usually within an hour.The second method was necessitated by the fact that primary amines are commonly sold as salts, more often as hydrochlorides. In these instances, the reaction was carried out in boiling solutions with sodium acetate.For both methods the course of the reactions was monitored by TLC or paper chromatography. The yields of the desired products were 60-80% of those calculated. The structures of products 1-52 were confirmed by elemental analysis and IR and PMR spectra. The IR spectra typically lacked absorption bands for aldehyde and contained absorption bands for C=N groups (1650 cm -1 ).During the synthesis of the cardenolide aldoximes we observed the rare case where two types of isomers, conformational (conformers) and geometrical (cis-trans or syn-anti), were formed simultaneously. The conformational isomers formed because free rotation around the C10-C19 single bond is restricted for steric reasons. We have previously reported this during the synthesis of cardenolide oximes [4] and demonstrated that the most stable of the two possible conformers is that in which the H atom of C19-H is oriented toward the angular methyl of the 18-CH 3 . This is completely consistent with the cardenolide aldimines and is confirmed by the following data. Strophantidin aldimines form complexes (green colored) with Cu ions that are soluble in organic solvents. The unshared pair of the N atom and the C3 and C5 OH groups (5) are involved in the complexation. The PMR spectra of the aldimines have signals for the angular 18-CH 3 methyl near 0.66-0.74 ppm, i.e., shifted to strong field. This is due to steric shielding of this group ...