Two new secoiridoid glucosides from Syringa velutina Kom

Chemical investigation of Syringa velutina Kom. led to the isolation of two new secoiridoid glucosides. Their structures were identified as 6'-0-(6, 7-dihyrofoliamenthoyl)-8-epi-kingisidic acid (syrveoside A, 1) and 6'-O-menthiafoloyl-8-epi-kingisidic acid (syrveoside B, 2) on the basis of chemical and physicochemical evidence.     

First total synthesis of (−)-8-epi-9-deoxygoniopypyrone

The structure and absolute configuration of natural 8-epi-9-deoxygoniopypyrone have been confirmed by an efficient and highly diastereoselective synthesis in 15 steps from (S)-mandelic acid with an overall yield of 43%.     

Studies directed toward synthesis of guanosine 8,5''-imino cyclonucleosides and derivatives—I

8,5'-Aminimino bridging in the guanosine series using 5'-O-tosyl (1) and 5'-O-mesyl derivatives (2) of 2',3'-O-isopropylidene-8-bromoguanosine (5) and hydrazine gave N³,5'-cyclized product 3 and the N⁵,5'-cyclonucleoside of 4-carboxyhydrazido-5-amino-2-bromoimidazole 4. To exclude the N³,5'-cyclization through ionization in the base moiety, a N²-dimethylaminomethylidene-N¹-methoxymethylene derivative 7 was synthesized from 5 through the N²-protected compound 6. 7 was converted into the N²-dimethylaminomethy analogue 8, which with hydrazine yielded first the N²-deprotected form of 8 (9). 8 or 9 with hydrazine under forcing conditions gave an 8,5'-aminimino-N¹-methox derivative 10. Oxidation of 10 with sodium metaperiodate or sodium nitrite yielded 8,5'-imino-N¹-methoxymethyleneguanosine (11a) and 8,5'-imino-N¹-methoxymethylenexanthosine derivative 11b, respectively. 11a was deprotected to 8,5'-imino-N¹-methoxymethyleneguanosine 12.     

Two new acetylated ginsenosides from the roots of Panax quinquefolium

Two new acetylated ginsenosides, 20（S）-protopanaxatriol-6-O-α-L-rhamnopyranosyl （1 → 2）-β-D-6＇-O-acetylglucopyranoside （1） and 20（R）-protopanaxatrol-6-O-α-L-rhamnopyranosyl （1 → 2）-β-o-6＇-O-acetylglucopyranoside （2）, were isolated from the roots of Panax quinquefolium. The structures were elucidated on the basis of spectroscopic techniques and chemical means.     

Two new glycosides from the seeds of Cassia obtusifolia

Two new glycosides,nor-rubrofusarin-6-O-β-D-(6′-O-acetyl)glucopyranoside(1) and 1-desmethylaurantio-obtusin-2-O-β-D-glucopyranoside (2) were isolated from the seeds of Cassia obtusifolia and their structures were established by chemical and spectral evidences.     

Synthesis of 14-epi-19-nor-22-oxa-1α,25-dihydroxyvitamin D3

The synthesis of 14-epi-19-nor-22-oxa-1α,25（OH）2D3 5 was started from diol 8 via Fall＇s method, oxidation, epimerization, protection, coupling with the 19-nor-A-ring 7, and then deprotection of the hydroxyl functions.     

Synthetic studies towards(-)-deserpidine:Total synthesis of the stereoisomer and derivative of (-)-deserpidine

The asymmetric synthesis of 16,17,20-epi-deserpidine and a derivative of(-)-deserpidine has been achieved.Key feature s in the assembly of the pentacyclic framework include a visible-light photocatalytic intra-/inter-/intramolecular radical cascade reaction to construct the tetracyclic ABCD ring system in one-pot and an intramolecularaldol reaction to forge the cyclohexane E ring.     

Isolation and structure elucidation of tsugicolines A-D, novel protoilludane sesquiterpenes from Laurilia tsugicola

Four novel Sesquiterpenes, tsugicolines A-D (1a, 2, 3a, 4), have been isolated from still cultures of the fungus Laurilia tsugicola (Basidiomycetae) Their structures were elucidated by means of chemical correlations and NMR studies and the relative configurations were established through a series of NOE difference spectra. The absolute configuration of tsugicoline A 1a (3-epi-illudol-5-one) was determined as 3S,6S,7R,9R,13S by the ‘partial resolution’ method of Horeau Treatment of tsugicoline A 1a with triethylamine in MeOH gave the metabolite 4; a possible mechanism is reported. Tsugicoline A is inactive on bacteria and fungi but inhibits the germination of the water cress Lepidium sativum.     

Total synthesis of the antimalarial naphthylisoquinoline alkaloid 5-epi-4′-O-demethylancistrobertsonine C by asymmetric Suzuki cross-coupling

The first total synthesis of the antimalarial naphthylisoquinoline alkaloid 5-epi-4′-O-demethylancistrobertsonine C (1a) and its—as yet unnatural—atropo-diastereomer, 1b, is described. The key step of the synthesis is the construction of the rotationally hindered and thus stereogenic biaryl axis, which was built up by a Suzuki reaction. The use of chiral ligands in the palladium-catalyzed cross-coupling permitted to increase the low internal asymmetric induction up to a diastereomeric ratio of 74:26. The assignment of the axial configurations of the atropo-diastereomers was achieved by 2D NMR experiments and corroborated by quantum chemical CD calculations.     

Crystal Structure of Nicotinic Acid(3,5-dinitrobenzoic Acid Organic Adduct

The title compound nicotinic acid(3,5-dinitrobenzoic acid(NDNT)has been obtained by the reaction of nicotinic acid with 3,5-dinitrobenzoic acid in deionic water at room temperature.The crystal is of monoclinic,space group P21/n with a=14.053(6),b=5.046(2),c=20.105(8)A,β=103.573(8)°,C13H9N3O8,Mr=335.23,Z=4,V=1385.8(10)A3,Dc=1.607g/cm3,μ(MoKα)=0.137 mm－1,F(000)=688,R=0.0435 and wR=0.0993 for 1239 observed reflections (I>2σ(I)).In the crystals,the asymmetric unit contains one nicotinic acid (C6H5NO2)and one 3,5-dinitrobenzoic acid (C7H4N2O6)molecules which are linked by some hydrogen bonds to form a twenty-membered hydrogen-bonded ring and an extended linear structure.     

Synthesis of (+)-carpamic acid from (+)-alanine

(+)-Carpamic acid [(2′R,5′S,6′S)-8-(5′-hydroxy-6′-methylpiperidin-2′-yl)octanoic acid, 1] was synthesized from (S)-alanine, employing intramolecular and reductive amination of acyclic amino ketone 8 as the key step to generate the piperidine ring.     

Crystal Structure of Nicotinic Acid·3,5-dinitrobenzoic Acid Organic Adduct

1INTRODUCTIONThedevelopmentofhighlyefficientnonlinearoptical(NLO)crystalsforvisibleandultraviolet(UV)regionsisextremelyimportantforbothlaserspectroscopyandlaserprocessing.Themainmeritsoforganicmaterialscomparedwithinorganiconesforsuchsecond-harmonicgenera…     

Diazotization of the amino acid [closo-1-CB9H8-1-COOH-6-NH3] and reactivity of the [closo-1-CB9H8-1-COO-6-N2]- anion

A comparative study of the reactivity of dinitrogen acids [closo-1-CB(9)H(8)-1-COOH-10-N(2)] (3[10]) and [closo-1-CB(9)H(8)-1-COOH-6-N(2)] (3[6]) was conducted by diazotization of a mixture of amino acids [closo-1-CB(9)H(8)-1-COOH-6-NH(3)] (1[6]) and [closo-1-CB(9)H(8)-1-COOH-10-NH(3)] (1[10]) with NO(+)BF(4)(-) in the presence of a heterocyclic base (pyridine, 4-methoxypyridine, 2-picoline, or quinoline). The 10-amino acid 1[10] formed an isolable stable 10-dinitrogen acid 3[10], while the 6-dinitrogen carboxylate 3[6](-) reacted in situ, giving products of N-substitution at the B6 position with the heterocyclic solvent (4[6]). The molecular and crystal structures for pyridinium acid 4[6]a were determined by X-ray crystallography. The electronic structures and reactivity of the 6-dinitrogen derivatives of the {1-CB(9)} cluster were assessed computationally at the B3LYP/6-31G(d,p) and MP2/6-31G(d,p) levels of theory and compared to those of the 10-dinitrogen, 2-dinitrogen, and 1-dinitrogen analogues.     

Quantitative analysis of metabolites in complex biological samples using ion-pair reversed-phase liquid chromatography-isotope dilution tandem mass spectrometry

A rapid, sensitive and selective ion-pair reversed-phase liquid chromatography-electrospray ionization isotope dilution tandem mass spectrometry (IP-LC-ESI-ID-MS/MS) was developed for quantitative analysis of free intracellular metabolites in cell cultures. As an application a group of compounds involved in penicillin biosynthesis pathway of Penicillium chrysogenum cells, such as penicillin G (PenG), 6-aminopenicillanic acid (6-APA), benzylpenicilloic acid (PIO), ortho-hydroxyphenyl acetic acid (o-OH-PAA), phenylacetic acid (PAA), 6-oxopipeidine-2-carboxylic acid (OPC), 8-hydroxypenicillic acid (8-HPA), L-alpha-(delta-aminoadipyl)-L-alpha-cystenyl-D-alpha-valine (ACV) and isopenicillin N (IPN) were chosen. (13)C-labeled analogs of the metabolites were added to the sample solutions as internal standards (I.S.). Sample mixtures were analyzed without any sample pretreatment. No extraction recovery check was needed because I.S. was added to the cell samples before extraction process. The method showed excellent precision (relative standard deviation (RSD)相似文献   

三种六氯铈(Ⅳ)酸有机盐的研究

合成了2,6-二甲基-γ-吡喃酮、咪唑和吡啶铈(Ⅳ)的氯化物,化学式为(C₇H₈O₂H)₂CeCl₆、(C₃H₄N₂H)₂CeCl₆和(C₄H₉NH)₄CeCl₈.采用差热、热重分析法比较了上述三种化合物的热稳定性,并配合以电导、红外、紫外光谱等手段进行了结构分析.     

Chelation of manganese(II) with quinaldic acids. An NMR relaxation study

Manganese(II) enhanced spin-lattice relaxation rates (1/T_1p) of ¹H and ¹³C nuclei in quinoline-2-carboxylic acid, 8-methoxyquinoline-2-carboxylic acid, 8-hydroxyquinoline-2-carboxylic acid, 8-aminoquinoline-2-carboxylic acid, and 6-(hydroxymethyl)pyridine-2-carboxylic acid were measured in aqueous solution at various temperatures. Relative metal-nucleus distances were calculated from the r^?6 dependence of 1/T_1p. The results indicate that the Mn²⁺ ion in the 8-methoxyquinaldic acid chelate is coordinated to the carboxyl oxygen atom and the nitrogen atom but not t the methoxyl oxygen atom.     

柳叶五层龙正丁醇提取部分中的3个新酚性成分及其α-葡萄糖苷酶抑制活性

采用多种色谱分离方法从柳叶五层龙(Salacia cochinchinensis Lour)的茎叶中分离得到5个化合物. 通过一维(1D)及二维核磁共振波谱(2D NMR), 包括核磁共振氢谱(¹H NMR)、 核磁共振碳谱(¹³C NMR)、 异核单量子相关(HSQC)、 异核多键相关(HMBC)、 氢氢相关(¹H-¹H COSY)和旋转坐标中的欧沃豪斯增强光谱(ROESY), 以及红外光谱(IR)和电喷雾电离高分辨质谱(ESI-HRMS)等方法, 鉴定其结构分别为Salaciacochinoside A(1), 5'-O-3,4,5-trimethoxybenzoyl-β-D-apiofuranoside(2), 5-methoxy-anticerol A(3), 21α,30-dihydroxy-D∶A-friedooleanan-3-one(4)和21α,26-dihydroxyfriedelan-3-one(5). 化合物1~3为新化合物. α-葡萄糖苷酶抑制活性测试结果显示, 化合物1和3对α-葡萄糖苷酶具有显著的抑制作用, 其IC₅₀值分别为0.32和0.59 μmol/L; 化合物2, 4和5未表现出α-葡萄糖苷酶抑制活性.     

Identification of Δ6-monounsaturated fatty acids in human hair and nail samples by gas-chromatography-mass-spectrometry using ionic-liquid coated capillary column

Lipids found in human sebum contain specific fatty acids such as sapienic (cis-6 16:1), cis-8 18:1 and sebaleic (cis-5, cis-8 18:2) acids. These fatty acids belong to the n-10 series and the initial step involved in their synthesis is the desaturation of palmitic acid by the Δ6-desaturase to form sapienic acid. The occurrence in human hair and nail of sapienic (cis-6 16:1), cis-8 18:1 and sebaleic (cis-5, cis-8 18:2) acids has not been reported to our knowledge nor has the formation of Δ6-monounsaturated fatty acids from other saturated fatty acids such as stearic acid. The pre-requisite for such identification is the ability to separate cis-6 from cis-8 monounsaturated fatty acid derivative (i.e. cis-6 18:1 from cis-8 18:1 methyl esters) by gas-chromatography (GC) and such separation is not achievable using cyanoalkyl based highly polar capillary columns. In the present study, we used the 100 m SLB-IL 111 ionic liquid based capillary column recently commercialized by Supelco (Bellefonte, PA). The identification was performed by gas-chromatography-mass-spectrometry (GC-MS) with electronic impact (EI) ionization using 4,4-dimethyloxazoline (DMOX) derivatives. Baseline separation between critical cis-6 18:1 and cis-8 18:1 isomers was obtained allowing unambiguous identification based on MS fragmentation and pure standards. In sebum, hair and nail samples, sapienic, cis-8 18:1 and sebaleic acids were found and more importantly, petroselinic acid was identified in these human tissues for the first time. In addition, we identified in hair and nail lipids cis-6 14:1, cis-6 15:1, iso-cis-6 16:1, aiso-cis-6 17:1 and cis-6 17:1 as their DMOX derivatives based on molecular ion as well as diagnostic ion fragments at m/z 167, 180 and 194. Possible biosynthesis scenario is postulated to explain the occurrence of these Δ6-monounsaturated fatty acids in human sebum, hair and nail lipids.     

Complex-induced proximity effects. Temperature-dependent regiochemical diversity in lithiation-electrophilic substitution reactions of N-BOC-2-azabicyclo[2.1.1]hexane. 2,4- and 3,5-methanoprolines

[reaction: see text] Azabicycle 4 and sec-butyllithium/TMEDA afford the C(1) bridgehead alpha-lithio anion at 0 degrees C. Anion quenching with carbon dioxide, methyl chloroformate, or DMF provide the bridgehead acid 8a (N-BOC-2,4-methanoproline), ester 8b, or aldehyde 8c, respectively. By contrast, at -78 degrees C these same reagents give a mixture of regioisomeric methylene and bridgehead anions whose quenching leads to mixtures of regioisomeric methylene and bridgehead acids 6a/8a, esters 6b/8b, or aldehydes 6c/8c, respectively. The previously unknown 3,5-methanoproline was prepared as its N-BOC methyl ester 6b.     

β分子筛中BrΦnsted酸分布及酸性强度的量子化学ONIOM理论计算研究

基于量子化学ONIOM [B3LYP/6-31G(d,p):UFF]计算方法,研究了β分子筛中BrΦnsted酸的落位及其酸性强度.计算采用22T簇模型,得到了不同酸性位的(Al,H)/Si替代能和质子亲和势.研究结果表明,BrΦnsted酸最有可能落位在Al(8)-O(11).Si(4),Al(8)-O(4)-Si(1),Al(7)-O(7)-Si(2)和Al(9)-O(6)-Si(3)位置.根据去质化能的计算,Al(7)-O(7)-Si(2)位置的酸性最强,A1(8)-O(11)-Si(4)的酸性最弱.酸性的强弱顺序为Al(7)-O(7)-Si(2)＞Al(9)-O(6)-Si(3)＞Al(8)-0(4)-Si(1)＞Al(8)-O(11)-Si(4).