Deacylation reactions of 20-acetyl dinorcholanic lactones and 20,23-diacetyl furost-22-enes

We report the deacylation of (20R)-20-acetyl-23,24-dinorcholanic lactones by hydrazine hydrate, under microwave irradiation in high yields. The elimination of the 20-acetyl group proceeded with retention of configuration which contrast with other proved deacylation methods that yield a mixture of diastereoisomers. In this way, unnatural (20R)-23,24-dinorcholanic lactones can be produced rapidly on a large scale. Both (20R)- and (20S)-lactones were prepared starting from diosgenin, hecogenin and sarsasapogenin, in 72-80% overall yields.     

开口箭甾体皂甙元的分离鉴定及其抗荔枝霜疫霉菌活性

在以荔枝霜疫霉菌为指示菌的生物活性测定导向跟踪下,运用TLC、硅胶柱层析、反相硅胶柱层析和凝胶柱层析等分离纯化方法,从开口箭(Tupistra chinensis)甲醇提取物的乙酸乙酯分部萃取物中分离纯化得到2个抗菌化合物。经现代光谱(MS、IR、1D NMR和2D NMR)分析,确定化合物1为1β,2β,3β,4β,5β,7α-六羟基螺甾-25(27)-烯-6-酮,化合物2为螺甾-25(27)-烯-1β,2β,3β,4β,5β,6β,7α-七醇。离体抗菌活性测定化合物1和化合物2抑制荔枝霜疫霉菌(Peronophythora litchii)孢子囊萌发的EC50分别为100.28 mg.mL-1和124.37 mg.mL-1。用质量浓度为500 mg.mL-1的两个化合物分别处理后接种霜疫霉菌,供试荔枝果实的发病率分别为16.7%和18.9%。     

Five new steroidal compounds from Ypsilandra thibetica

Five new steroids, including the four new steroidal saponins ypsilandroside B (1), ypsilandroside A (2), isoypsilandroside A (4), and isoypsilandroside B (5), as well as the new steroidal sapogenin isoypsilandrogenin (3), were isolated from the whole plant of Ypsilandra thibetica Franch. Their structures were determined on the basis of spectroscopic analyses, including extensive 2D-NMR techniques. The structure and relative configuration of ypsilandroside B (=(3beta,12alpha,25R)-3-[(alpha-L-rhamnopyranosyl-(1-->2)-beta-D-apiofuranosyl)oxy]spirost-5-ene-12,27-diol; 1) was unequivocally determined by single-crystal X-ray diffraction. The antifungal and antibacterial activities of 1-5 towards various types of fungi and bacteria are reported.     

3,4-Seco-spirostane sapogenins with cytotoxic activity from Allium umbilicatum boiss

Two new sapogenins, named seco-umbilicagenins A and B (1 and 2), possessing a new chemical structure based on a 3,4-seco-spirostane skeleton, were isolated from Allium umbilicatum Boiss. The chemical structures of seco-umbilicagenins A and B were established through a combination of extensive spectroscopic analysis, mainly nuclear magnetic resonance spectroscopy and mass spectrometry, and chemical methods as (2S,25R)-2,5α,6β-trihydroxy-3,4-seco-spirosta-3,4-dioic acid (1) and (2S,25R)-2,4,5α-trihydroxy-6-oxo-3,4-seco-spirostan-3-oic acid (2). Interestingly, the isolated compounds exhibited cytotoxic activity on J-774, murine monocyte/macrophage, and WEHI-164, murine fibrosarcoma, cell lines. To the best of our knowledge this is the first time that 3,4-seco-spirostane sapogenins are isolated from natural sources, being this skeleton obtained by synthetic modification of intact sapogenins.     

The resolution of 25α- and 25β-spirosta-3,5-dienes from sapogenin yielding plants

The separation of the artefacts, 25α- and 25β-spirosta-3,5-dienes, is described and their individual characters are recorded. Following acid hydrolysis of plant material the ratios of diene to sapogenin and of 25α- to 25β-diene varied with different species and morphological parts. The 25α-diene commonly predominated as did diosgenin over yamogenin. Diene production is reduced when, before undergoing acid hydrolysis, the plant material is incubated with water for increased sapogenin yield. The label from acetate-2-¹⁴C was found predominantly in the 25α-diene from such an incubation-acid hydrolysis experiment.