Lumutinines A-D, linearly fused macroline-macroline and macroline-sarpagine bisindoles from Alstonia macrophylla

Four new linearly fused bisindole alkaloids, lumutinines A-D (1-4), were isolated from the stem-bark extract of Alstonia macrophylla. Lumutinines A (1) and B (2) represent the first examples of linear, ring A/F-fused macroline-macroline-type bisindoles, while lumutinines C (3) and D (4) were constituted from the union of macroline and sarpagine moieties. A reinvestigation of the stereochemical assignment of alstoumerine (8) by NMR and X-ray diffraction analyses indicated that the configuration at C-16 and C-19 required revision.     

Sesquiterpenoids from Incarvillea arguta: absolute configuration and biological evaluation

Diincarvilones A-D (1-4), incarvilone A (5), and a known compound, argutosine B (6), were isolated from Incarvillea arguta. The structures, including the absolute configurations of the new compounds, were determined by NMR spectroscopy, X-ray diffraction analysis, CD spectroscopy, and a variety of computational methods. The biological properties of these substances, including effects on intracellular Ca(2+) influx, nitric oxide (NO) production, and human cancer cells, were evaluated. The results showed that at the concentration of 10 μM (in HBSS buffer) diincarvilones A and B cause a persistent increase in cytoplasmic calcium levels in A549 cells.     

Structure and absolute configuration of new diterpenes from Lavandula multifida

Four new diterpenes (1-4) have been isolated from the aerial parts of Lavandula multifida, together with the known compound glutinosin (5). The structures of these compounds were identified on the basis of extensive NMR studies as 15,16-dihydroxy-7,11-dioxopimar-8(9)-ene (1), 15S,16-dihyroxy-7-oxopimar-8(9)-ene (2), 15,16,17-trihydroxy-7-oxopimar-8(9)-ene (3), and 15,16,17-trihydroxypimar-8(9)-ene (4). The absolute configuration of the 15,16-diol moiety in 1-5 was determined observing the circular dichroism induced after addition of dimolybdenum tetracetate in DMSO solution.     

Strychnan and secoangustilobine A type alkaloids from Alstonia spatulata. Revision of the C-20 configuration of scholaricine

A total of 25 alkaloids were isolated from the leaf and stem-bark extracts of Alstonia spatulata, of which five are new alkaloids of the strychnan type (alstolucines A-E, 1-5) and the other, a new alkaloid of the secoangustilobine A type (alstolobine A, 6). The structures of these alkaloids were established using NMR and MS analysis and, in the case of alstolucine B (2), also confirmed by X-ray diffraction analysis. A reinvestigation of the stereochemical assignment of scholaricine (13) by NMR and X-ray analyses indicated that the configuration at C-20 required revision. Alkaloids 1, 2, 6, 7, 9, 10, and 13 reversed multidrug resistance in vincristine-resistant KB cells.     

Diversonol and blennolide derivatives from the endophytic fungus Microdiplodia sp.: absolute configuration of diversonol

Chemical investigation of the fungal strain Microdiplodia sp. isolated from the shrub Lycium intricatum led to the isolation of four new compounds: a hexahydroxanthone (2), a 2,3-dihydrochroman-4-one (3), a 7-oxoxanthone derivative (4), and a 1,4-oxazepan-7-one (5). The relative configurations of the new compounds were determined by intensive NMR investigations, notably NOESY experiments at different temperatures. The absolute configurations of the well-known fungal metabolite diversonol (1) and of other xanthone derivatives (3, 4) were established by means of TDDFT ECD calculations. Most of the metabolites were biologically active, with antibacterial activity against Legionella pneumophila and/or antifungal activity against Microbotryum violaceum.     

天然产物绝对构型的确定（英文）

天然产物结构研究一直是天然药物化学相关领域最重要的工作之一,尤其对天然产物绝对构型（AC）的确定更是具有挑战性的研究内容,目前得到国内外学者越来越多的关注。在过去的几十年里已发展了许多技术和方法用来确定天然产物的绝对构型,包括直接法（或绝对方法）,例如X射线单晶衍射（XRD）、电子圆二色谱（ECD）、振动圆二色谱（VCD）及拉曼光学活性（ROA）;使用已知绝对构型的参照物或衍生化试剂的间接法（或相对方法）,例如利用经验规则的圆二色谱,以及利用手性衍生化试剂各向异性效应的核磁共振法（NMR）。但由于这些方法适用的化合物类型和结构不尽相同,目前尚没有一种通用技术涵盖所有类型天然产物绝对构型的测定,我们只能灵活应用各种技术和方法才能确定大部分天然产物的绝对构型。本综述总结了大多数当前天然产物绝对构型测定中常用的以及具有潜在前景的技术和方法,并简要介绍了它们的原理及特点。     

Isolation and absolute configuration of ent-Halimane diterpenoids from Hymenaea courbaril from the Suriname rain forest.

Bioactivity-directed fractionation of a methanol extract of Hymenaea courbaril afforded the three new diterpenoids (13R)-13-hydroxy-1(10),14-ent-halimadien-18-oic acid (1), (2S,13R)-2,13-dihydroxy-1(10),14-ent-halimadien-18-oic acid (2), and (13R)-2-oxo-13-hydroxy-1(10),14-ent-halimadien-18-oic acid (3). The configurations of these compounds were determined from X-ray crystallography of 1, circular dichroism of 2 and 3, and spectral studies of prepared derivatives. Compound 1 exhibited weak cytotoxicity toward the 1138 mutant yeast strain and the A2780 human ovarian cancer cell line.     

Resolution and absolute configuration of naturally occurring auronols

Resolution of racemic 2-benzyl-2-hydroxy-1-benzofuran-3(2H)-ones (auronols) and CD data of the ensuing enantiomers permit assessment of the absolute configuration at the single stereocenter.     

Enantiomeric derivatives of tokinolide B: absolute configuration and biological properties

The enantiomeric lactams (-)-8, (+)-8, (+)-9, and (-)-9 were formed by the reaction of the dimeric phthalide rac-tokinolide B (rac-3) with (R)-(+)-α-methylbenzylamine and (S)-(-)-α-methylbenzylamine. The absolute configurations of compounds 8 and 9 were assigned by experimental and theoretically calculated electronic circular dichroism methods for (+)-8 and (-)-9. Compounds 3, 5, (-)-8, (+)-8, (+)-9, and (-)-9 displayed cytotoxic activity toward several human tumor cell lines, with (-)-8 and (-)-9 being the most potent.     

Neoclerodane diterpenoids from Teucrium montbretii subsp. libanoticum and their absolute configuration

From the aerial parts of Teucrium montbretii subsp. libanoticum 10 neoclerodane diterpenoids were isolated. Three of them are new [3beta-hydroxyteubutilin A (1), 12-epi-montanin G (2), 20-epi-3,20-di-O-deacetylteupyreinidin (3)], whereas the other seven, namely, 6-ketoteuscordin (4), teuscordinon (5), 6beta-hydroxyteuscordin (6), montanin D (7), 3,20-di-O-deacetylteupyreinidin (8), montanin G (9), and 3-O-deacetylteugracilin A (10), are previously known structures. The structures of 1-3 were determined by spectral and chemical methods.     

Xestoproxamines A-C from Neopetrosia proxima. Assignment of absolute stereostructure of bis-piperidine alkaloids by integrated degradation-CD analysis

The complete stereostructures of xestoproxamines A-C, from the Bahamian sponge Neopetrosia proxima, were assigned from spectroscopic analysis, including MS, 2D NMR, and integrated degradation-CD analysis. Two new CD application protocols are described for defining absolute configuration: one for allylic methyl groups in branched chains and a second for the heterocyclic core bis-piperidine with specific applicability to other members of this class alkaloids--known for their stereoheterogeneity--and tertiary cyclic amines in general.     

灯台树叶中鸭脚树叶碱型生物碱

目的：研究云南当地药材灯台树的化学成分．方法：运用硅胶柱色谱分离，光谱技术（核磁共振，红外，紫外和质谱）鉴定结构。结果：从灯台树叶中分离到4个鸭脚树叶碱类型的单萜吲哚生物碱：5β-methoxyaspidophylline（1），鸭脚树叶碱（2），鸭脚树叶醛（3），5-methoxystrictamine（4）．结论：1是一个新化合物.     

Structure and absolute configuration of helosides A and B, new saponins from Chamaelirium luteum

Investigation of Chamaelirium luteum roots led to the isolation of two new steroidal saponins, helosides A and B, that contain a previously unreported aglycone, helogenin. Their structures and absolute configuration were elucidated through MS-MS, NMR, chemical degradation, and X-ray crystallography.     

Sarcochromenol sulfates A-C and sarcohydroquinone sulfates A-C, new natural products from the sponge Sarcotragus spinulosus.

New Na+,K(+)-ATPase inhibitors, sarcochromenol sulfates A [1], B [2], and C [3] and sarcohydroquinone sulfates A [4], B [5], and C [6], have been isolated from the sponge Sarcotragus spinulosus. Four of them (1, 4-6) and all six corresponding acetates 1a-6a have been isolated, and their structures have been established by spectral methods and chemical transformations.     

New indole alkaloids from the bark of Alstonia scholaris

A new indole alkaloid, akuammiginone (1), and a new glycosidic indole alkaloid, echitamidine-N-oxide 19-O-beta-d-glucopyranoside (2), together with the five known alkaloids, echitaminic acid (3), echitamidine N-oxide (4), N(b)-demethylalstogustine N-oxide (5), akuammicine N-oxide (6), and N(b)-demethylalstogustine (7), were isolated from the trunk bark of Alstonia scholaris collected in Timor, Indonesia. The structures of all compounds were elucidated by spectroscopic methods. This is the first report of compounds 3-5and 7 in A. scholaris. Some NMR assignments of the known compounds were revised.     

Pipestelides A-C: cyclodepsipeptides from the Pacific marine sponge Pipestela candelabra

Pipestelides A-C (2-4) are three new NRPS-PKS hybrid macrolides containing uncommon moieties, isolated from the Pacific marine sponge Pipestela candelabra. Their structures were elucidated on the basis of spectroscopic data. These cyclodepsipeptides appear to be biosynthetically related to jaspamide (aka jasplakinolide) (1) by chemical modification of the building blocks of the polyketide or peptide chains. Pipestelides A-C (2-4) contain a bromotyrosine [3-amino-3-(bromo-4-hydroxyphenyl)propanoic acid] unit, a polypropionate with a Z double bond, and a 2-hydroxyquinolinone, respectively. Revised chemical shift assignments are provided for the co-isolated known jasplakinolide C(a) (5). In addition, compounds 2 and 3 exhibited cytotoxic activities in the micromolar range.     

Isolation and structure of the cytotoxin lyngbyabellin B and absolute configuration of lyngbyapeptin A from the marine cyanobacterium Lyngbya majuscula

An analogue of the potent microfilament-disrupter lyngbyabellin A (1) has been isolated as a minor metabolite from the marine cyanobacterium Lyngbya majuscula collected at Apra Harbor, Guam. It possesses slightly weaker cytotoxicity than 1 and has been named lyngbyabellin B (2). Primarily NMR spectroscopy was used to determine its structure. The absolute configuration of 2 has been ascertained by chiral HPLC analysis of degradation products and by comparison with lyngbyabellin A (1). The known modified tetrapeptide lyngbyapeptin A (3) has also been found in the same extract, and its absolute stereochemistry could be determined for the first time.     

Structure and absolute configuration of clerodane diterpene glycosides and a rearranged cadinane sesquiterpene glycoside from the stems of Tinospora sinensis

Three new clerodane diterpene glycosides, tinosposinensides A-C ( 1- 3), and a new rearranged cadinane sesquiterpene glycoside, tinosinenside ( 4), were isolated from the stems of Tinospora sinensis. The structure including the relative configuration was elucidated on the basis of spectroscopic analysis. The absolute configuration was determined by application of the modified Mosher's method and chemical transformation. The inhibitory activities of the isolated compounds against alpha-glucosidase are also described.