利用薯蓣皂甙元完整骨架合成偏诺皂甙元

报道了从薯蓣皂甙元合成偏诺皂甙元, 偏诺皂甙元是中药重楼的生物活性成分的甙元. 合成方法展现了利用资源性化合物的一个新策略, 即充分合理地利用起始原料的完整骨架和全部官能团的思想在转化薯蓣皂甙元成偏诺皂甙元的过程中得以实现. 合成的关键步骤是区域选择性转化胆甾-5-烯-16,22-二酮-3,26-二醇成为胆甾-5,16-二烯-22-酮-3,26-二醇. 此关键反应步骤也可用于cephalostatin 和 OSW-1的合成.     

3β,26-二乙酰氧基-5,16-二烯-胆甾-22-酮的合成

云南丰产生物资源薯蓣皂甙元与重楼的活性成分偏诺皂甙元(Ⅰ)、克里普托皂甙元(Ⅱ)以及从非洲南部的虎眼万年青中分离得到的抗肿瘤活性物质OSW-1(Ⅲ)[1,2]具有相同的骨架,若利用薯蓣皂甙元完整碳骨架合成化合物Ⅰ～Ⅲ,其关键是在15,16位引入一个碳碳双键[3],再经结构修饰可实现Ⅰ～Ⅲ的合成,本文报道可用于合成上述化合物Ⅰ～Ⅲ的关键中间体3β,26-二乙酰氧基-5,16-二烯-胆甾-22-酮的合成,产物并经IR,1H NMR,13C NMR,EI-MS,HRMS所证实,总收率在30%左右.     

利用薯蓣皂甙元完整骨架形式合成1α,25-二羟基维生素D3

首次利用薯蓣皂甙元的完整骨架经16步反应以7.6%的总收率合成了骨化三醇(1α,25-二羟基维生素D₃)的光化反应前体. 3-苄基保护的薯蓣皂甙元经还原开E/F环产生3,16,26-胆甾三醇-3-苄醚(5). 除去化合物5 C-16羟基后, 其C-26羟基经消除和羟基化反应转移到C-25位. 目标分子A/B环结构单元通过薯蓣皂甙元A/B环的官能团转化被构筑. 按照已知的光化反应, (1S,3R)-胆甾-5,7-二烯-1,3,25-三醇能被转化成为1α,25-二羟基维生素D₃.     

资源化学研究进展*

本文总结了本课题组在资源化学领域的研究工作进展,内容涉及到天然资源化合物甾体皂甙元和非天然资源性化合物氟烷基磺酰氟的反应及其在有机合成中的应用。首先介绍了原子经济性地利用甾体皂甙元资源的策略与方法。为解决甾体皂甙元资源在工业利用过程产生的环境污染和资源浪费问题,我们发展了用30%双氧水代替铬酐氧化降解假甾体皂甙元的方法,使“百分之百”利用甾体皂甙元资源的理想成为现实。双氧水与乙酸原地产生的过氧酸直接氧化甾体皂甙元成为孕甾-16,20-二醇类化合物和4R-甲基-5羟基戊酸内酯,通过甾体皂甙元的非正常Baeyer-Villiger反应合成了甾体-16羟基-22-内酯类化合物和3R-甲基-5羟基戊酸内酯。所获甾体中间体和带甲基侧链的双官能团手性试剂被应用于部分甾体药物、昆虫信息素、香料和天然产物的合成中。另外还介绍了利用甾体皂甙元完整骨架合成目标分子的资源性化合物利用策略。本文第二部分内容介绍了氟烷基磺酰氟资源利用的策略和方式。反应共生是我们提高氟烷基磺酰氟资源利用率的新思路,基于共生反应概念,研究了邻二醇环氧化反应、烯烃环氧化反应和碳正离子重排等反应与氟烷基磺酰氟水解反应的共生反应,并且介绍了其合成应用实例。     

狭叶地榆化学成分研究

从狭叶地榆根中分离出7种化合物,经化学和光谱方法鉴定分别为2,4-二羟基-6-甲氧基苯乙酮(Ⅰ)、3,3′,4-三(○-甲基)逆没食子酸(Ⅱ)、3,4′,4-三(○-甲基)逆没食子酸(Ⅲ)、地榆皂甙元(Ⅳ)、地榆皂甙Ⅰ(Ⅴ)、地榆皂甙Ⅱ(Ⅵ)和胡萝卜甙(Ⅶ),其中Ⅰ为首次从天然界中得到,Ⅲ为一新化合物。     

液相色谱-电喷雾电离质谱与电子轰击质谱联用筛选百合中的甾体皂甙

 利用高效液相色谱 电喷雾电离质谱联用仪 (HPLC/ESI MS)、电子轰击质谱 (EI MS)和半制备型高效液相色谱 ,从卷丹百合中筛选出了两种甾体皂甙 ,其中一种为含有 3个糖基与提果皂甙元的甾体皂甙 ,另一种为含有 3个糖基和薯蓣皂甙元的甾体皂甙。结果表明 :在线的HPLC/ESI MS能够准确快速地提供糖甙类化合物的分子质量和糖链部分的有益信息 ,但对甙元部分提供的信息极少 ;离线的EI MS只需极少量 (1mg～ 2mg)的纯品就能准确地提供甙元部分的有益信息 ,但很难获得糖甙的分子离子峰与糖链部分的信息 ,两者有机地结合起来能快速地从植物中筛选甾体皂甙。     

利用薯蓣皂甙元完整骨架合成澳洲茄胺

澳洲茄胺1是中药龙葵生物活性成分澳洲茄碱和澳洲茄边碱的甙元, 具有抗肿瘤等生物活性. 利用薯蓣皂甙元的完整骨架, 以16-羟基甾体皂甙元的溴代开环反应为关键反应, 经9步反应, 以21%的总收率完成了澳洲茄胺1的合成.     

由孕甾-3S,5R,6R,16S,20S-五醇合成黄体酮

首次利用薯蓣皂甙元降解产物, 孕甾-3S,5R,6R,16S,20S-五醇(3)完成了黄体酮的合成. 孕甾-3S,5R,6R,16S,20S-五醇可方便地通过薯蓣皂甙元经由30%双氧水原地产生的过酸氧化降解得到. 它经过缩酮化反应、乙酰化反应和串联的脱缩酮-溴代乙酰化反应被转化成关键合成中间体16R-溴孕甾-3S,5R,6R,20S-四醇-3,6,20-三乙酸酯(6). 化合物6经锌粉还原、C-3乙酰氧基选择性水解氧化反应和C-5羟基消除反应生成6R,20S-二乙酰氧基孕甾-4-烯-3-酮(10). 化合物10经C-6乙酰氧基还原和C-20乙酰氧基水解-氧化生成目标分子黄体酮. 合成经10步反应, 反应总收率达45.1%.     

龙舌兰属植物中甾族皂甙元的研究——Ⅱ.剑麻中甾族皂甙元的分离和鉴定

从海南岛栽培的剑麻叶中分离出10个已知的甾族化合物,即新替告皂甙元酮(II,Neo-tigogenone)、β-谷甾醇(V,β-Sitosterol)、新替告皂甙元(VI_a,Neotigogenin)、替告皂甙元(VI_b,Tigogenin)、剑麻皂甙元(VII_a,Sisalagenin)、海柯皂甙元(VII_b,Hecogenin)、5α-娠烷-3β、20β-二醇(IX,5a-Pregnan-3β,20β-diol)、洛柯皂甙元(X,Rockogenin)、12-表洛柯皂甙元(XI,12-Epirockogenin)和绿莲皂甙元(XVI,Chlorogenin)以及两个新的三羟基甾族皂甙元,即海南皂甙元(Hainangenin)和红光皂甙元(Hongguanggenin),根据质谱和核磁共振谱,这两个新皂甙元的结构初步分别定为3β,6α,23β-三羟基-5α,25R-螺甾烷(XVIII_a)和3β,6α,23α-三羟基-5α,25R-螺甾烷(XVIII_b),两者为C_(23)位的差向异构体。     

基于正交试验与化学子空间法研究中药重楼中甾体皂甙的提取工艺

重楼为百合科植物云南重楼或七叶一枝花的干燥根茎,用于治疗疮痈肿、咽喉肿痛、毒蛇咬伤、跌扑伤痛和惊风抽搐等[1]。其主要药效成分为甾体皂甙,其中又以薯蓣皂甙和偏诺皂甙等两种皂甙的含量最多。皂甙的提取方法主要有浸渍法[2]、加热回流法[3]以及超声法[4,5]等,其中超声法以     

Synthesis of pennogenyl saponins using three methods

The synthesis of pennogenyl saponins using three important methods of glycosylation is reported in this article. Six correlative compounds (7–12) were first synthesized. As donors (1–6), glycosyl halide, trichloroimidate, and thioglycoside were chosen to study their reaction with the acceptor pennogenin. In these reactions the difference in steric hindrance between 3-OH and 17-OH of pennogenin was utilized skillfully and only the 3-hydroxyl group of pennogenin could be connected with each kind of donors selectively. There was no reaction at the 17-hydroxyl group, which had no protection. The characteristic above makes it convenient to synthesize compounds of pennogenyl saponins. Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 348–350, July–August, 2007.     

Synthesis of pennogenyl saponin analogs using three methods

The synthesis of pennogenyl saponins and related compounds using three popular methods of glycosylation has been reported for the first time. Glycosyl halides, glycosyl trichloroacetimidates, and thioglycosides were used as glycosyl donors in the reactions with pennogenin as the glycosyl acceptor. The reactions occur selectively with the C(3)OH group due to the difference in steric accessibility of the hydroxyl groups at the C(3) and C(17) atoms of pennogenin. This makes it possible to synthesize a series of pennogenyl saponins without C(17)OH group protection. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1789–1792, October, 2006.     

An improved synthesis of pennogenin

An improved synthesis of pennogenin, a bioactive component of Chinese herb “Chonglou” (Paris), is described. A ring-switching process opened the ring E of diosgenin and allowed the use of a hydroxyl-directed diboration/oxidation to introduce C17α-OH, hence eliminating the use of OsO₄. This strategy might be rendered to synthesize similar steroids with C17α-OH.     

Identification of chemical constituents in Rhizoma Paridis Saponins and their oral administration in rat plasma by UPLC/Q‐TOF/MS

On‐line ultra‐performance liquid chromatography (UPLC) coupled with diode‐array detection (UPLC/DAD) and electrospray ionization quadrupole time‐of‐flight mass spectrometry (ESI‐Q‐TOF‐MS) were used for separation, identification and structural analyses of saponins in Rhizoma Paridis saponins (RPS) and rat plasma after oral administration of RPS. Thirty steroidal saponins in RPS were identified by comparing their retention time, accurate mass measurement and positive and negative mass spectrometry data with that of reference compounds. The UPLC/Q‐TOF‐MS method was proved to be rapid and efficient in that 30 steroidal saponins, including three kinds of saponins (prototype, pennogenyl and diosgenyl saponins) were tentatively characterized within 6 min. After oral administration of RPS, 21 original saponins were absorbed in RPS‐treated rat plasma. Our results indicated that UPLC/Q‐TOF‐MS is a rapid and effective tool for identification of a series of saponins at trace level. Copyright © 2010 John Wiley & Sons, Ltd.     

Facile synthesis of trisaccharide moiety corresponding to antitumor activity in triterpenoid saponins isolated from Pullsatilla roots

A trisaccharide found in triterpenoid saponins isolated from Pullsatilla roots appears as an important promoiety for the enhancement of anticancer activity of their aglycones. Thus a facile synthetic method for a trisaccharide moiety, allyl-2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->2)-[2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->4)]-3-O-benzoyl-beta-L-arabinopyranoside (3), has been firstly developed through the regio- and stereoselective glycosylations from arabinose in total 16% yield via route 2 (eight steps). In this synthetic procedure, the protection of anomeric -OH of L-arabinose with equatorially oriented allyl group unlike with the axial 4-methoxybenzyl protecting group well promoted glycosyl bond formation between alpha-L-rhamnopyranosyl trichloroacetimidate and 2-OH of arabinose. As expected, the synthesized trisaccharide moiety 3 has no cytotoxicity (ED50: >100 microM) against three human cancer cell lines (A-549, SK-OV-3, and SK-MEL-2), respectively.     

Studies on the synthesis of landomycin A: synthesis and glycosidation reactions of L-rhodinosyl acetate derivatives

An efficient, eight-step synthesis of L-rhodinosyl acetate derivative 3 is described. The synthesis originates from methyl (S)-lactate and involves a highly stereoselective, chelate-controlled addition of allyltributylstannane to the lactaldehyde derivative 7. The beta-anomeric configuration of 3 was established with high selectivity by acetylation of the pyranose precursor with Ac(2)O and Et(3)N in CH(2)Cl(2). Preliminary studies of glycosidation reactions of 3 and L-rhodinosyl acetate 10 containing a 3-O-TES ether revealed that these compounds are highly reactive glycosidating agents and that trialkylsilyl triflates are effective glycosylation promoters. The best conditions for reactions with 15 as the acceptor involved use of diethyl ether as the reaction solvent and 0.2 equiv of TES-OTf at -78 degrees C. However, the TES ether protecting group of 10 proved to be too labile under these reaction conditions, and mixtures of 16a, 17, and 18a are obtained in reactions of 10 and 15. Disaccharide 17 arises via in situ cleavage of the TES ether of disaccharide 16a, while trisaccharide 18a results from a glycosidation of in situ generated 17 (or of 16a itself) with a second equivalent of 10. These problems were largely suppressed by using 3 with a 3-O-TBS ether protecting group as the glycosyl donor and 0.2 equiv of TES-OTf as the reaction promoter. Attempts to selectively glycosylate the C(3)-OH of diol acceptors 20 or 28 gave a 70:30 mixture of 21 and 22 in the reaction of 20 and a 43:27:30 mixture of regioisomeric trisaccharides 29 and 30 and tetrasaccharide 31 from the glycosidation reaction of 28. However, excellent results were obtained in the glycosidation of differentially protected disaccharide 34 using 1.5 equiv of 3 and 0.05 equiv of TBS-OTf in CH(2)Cl(2) at -78 degrees C. The latter step is an important transformation in the recently reported synthesis of the landomycin A hexasaccharide unit.     

Convenient temporary methyl imidate protection of N-acetylglucosamine and glycosylation at O-4

This paper expands on the scope and utility of the temporary conversion of N-acetyl groups to alkyl imidates when attempting to glycosylate at O-4 of N-acetylglucosamine acceptors. The optimized synthesis of alkyl imidate protected glucosamine acceptors at position 4 and carrying various protecting groups at O-3 is described. These imidates were prepared immediately prior to glycosylation by treating the 4-OH acceptors with 0.5 M MeOTf to obtain the corresponding methyl imidates still carrying a free 4-OH group. When preparing these imidates in diethyl ether as the reaction solvent, we observed the unexpected formation of ethyl imidates in addition to the desired methyl imidates. While the 3-O-allyl acceptors were too unstable to be useful in glycosylation reactions, the 3-O-acylated methyl and ethyl imidates of glucosamine were shown to behave well during the glycosylation of the 4-OH with a variety of reaction conditions and various glycosyl donors. Glycosylation of these acceptors was successfully carried out with perbenzylated beta-thioethyl rhamnopyranoside under MeOTf promotion, while activation of this donor under NIS/TMSOTf or NIS/TfOH proved less successful. In contrast, activation of the less reactive perbenzylated alpha-thioethyl and peracetylated beta-thioethyl rhamnopyranosides with NIS/TfOH led to successful glycosylations of the 4-OH. Activation of a peracetylated rhamnosyl trichloroacetimidate by TMSOTf at low temperature also gave a high yield of glycosylation. We also report one-pot glycosylation reactions via alkyl imidate protected acceptor intermediates. In all cases the alkyl imidate products were readily converted to their corresponding N-acetyl derivatives under mild conditions.     

Crystal and molecular structure of (25R)-spirost-5-ene-3β,17α-diol 3,17-diacetate (pennogenin diacetate)

An x-ray structural investigation has been made of pennogenin diacetate (diffractometer, direct method, anisotropic refinement, R factor 0.050). The spatial structure of the molecule has been established. The acetylation of the hydroxy group in position 17α in pennogenin is connected with the steric hindrance arising between the atoms of the acetoxy group and the atoms of ring D. Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 689–693, September–October, 1991.     

Analysis of variations in the contents of steroidal saponins in Fructus Tribuli during stir-frying treatment

Just as natural saponins transform into aglycones, secondary glycosides and their derivatives using biotransformation technology, steroidal saponins may also undergo similar transformation after stir-frying. The purpose of this study was to elucidate the variations and the reasons for these variations in the contents of steroidal saponins in Fructus Tribuli (FT) during a stir-frying treatment. Stir-fried FT was processed in different time–temperature conditions. An UHPLC–MS/MS method was established and fully validated for quantitative analysis. In addition, the simulation processing products of tribuluside A, terrestroside B, terrestrosin K, terrestrosin D and 25R-tribulosin were determined by qualitative analysis using UHPLC–Q-TOF–MS. The established UHPLC–MS/MS method provides a rapid, flexible, and reliable method for the quality assessment of FT. The present study revealed that furostanol saponins with a C22-OH group could transform into corresponding furostanol saponins with a C-20–C-22 double bond (FSDB) via dehydroxylation. Additionally, FSDB could be successively converted into its secondary glycosides via a deglycosylation reaction. The transformation of spirostanol saponins into corresponding aglycones via deglycosylation led to a decrease in spirostanol saponins and an increase in aglycones. The results of this research provided scientific evidence of variation and structural transformation among steroidal saponins. These findings might be helpful for elucidating the processing mechanism of FT.