Polyketides from a marine sponge-derived fungus Mycelia sterilia and proton-proton long-range coupling

A series of polyketide-originated metabolites (1-5) were isolated from a marine sponge-derived fungus Mycelia sterilia. Of these, 1-3 were new compounds. Their structures were elucidated by spectroscopic methods as (4R*, 5S*, 6S*, 8S*, 13R*)-1-(2,8-dihydroxy-1,2,6-trimethyl-1,2,6,7,8,8a-hexahydro-naphthalen-1-yl)-3-methoxy-propan-1-one (1), 4,8-dihydroxy-7-(2-hydroxy-ethyl)-6-methoxy-3,4-dihydro-2H-naphthalen-1-one (2) and 1-methyl-naphthalene-2,6-dicarboxylic acid (3). In 1, the proton-proton long-range coupling phenomenon claimed attention and was discussed.     

Structural assignment of regioisomeric 3-[2- or 5-anilino-2-(alkylamino)phenyl]propanoic acids, 2H-1,4-benzothiazin-3(4H)-ones and 2,3-dihydro-1,5-benzothiazepin-4(5H)-ones by 1D NOE and gHMBC NMR techniques

The 1H and 13C NMR spectra of compounds 1-11 and 16-22 in CDCl3 and DMSO-d6 solutions allowed structural assignment to regioisomers 1/5 and 2/6 and their regioselective cyclization products 16-18 utilizing one- and two-dimensional NMR techniques (APT, DEPT, NOE difference, COSY, NOESY, HETCOR and gHMQC, gHMBC). Temperature-dependent 1H NMR spectra of 8-anilino-5-(4-methyl-2-pentyl)-2,3-dihydro-1,5-benzothiazepin-4(5H)-one (18) indicated a free energy of activation (deltaG++) of ca 17 kcal mol(-1) for interconversion between rotamers. The 1H and 13C NMR spectra of 20 and 22 containing two chiral centers exhibit duplication of several signals, indicating the existence of two diastereomeric forms. The structure of 4 was unambiguously confirmed by x-ray crystallography.     

面包酵母对1, 4, 4α, 8α-四氢-1, 4-亚甲基萘-5, 8-二酮的催化异构化

文章描述了面包酵母将1, 4, 4α, 8α-四氢-1, 4-亚甲基萘-5, 8-二酮催化异构化为1, 4-二氢-5, 8-二羟基-1, 4-亚甲基萘, 而不是还原为相应的羟基化合物。     

Spectral assignments for the aldose reductase inhibitor 4(S)-2,3-dihydro-6-fluoro-2(R)-methylspiro[chroman-4,4'-imidazoline]-2',5'-dione and its synthetic intermediates

The 1H and 13C NMR chemical shifts of the aldose reductase inhibitor 4(S)-2,3-dihydro-6-fluoro-2(R)-methylspiro[chroman-4,4'-imidazoline]-2',5'-dione, methylsorbinil, and its seven synthetic intermediates, have been completely assigned on the basis of DEPT, COSY, g-HSQC and g-HMBC. All C--F coupling constants from one-bond to four-bond in the 13C NMR spectra and H--F and H--H coupling constants from three-bond to four-bond in 1H spectra were obtained.     

Structure determination of ramosine, a guaianolide, by NMR spectroscopy

Ramosine, a new sesquiterpene lactone, was isolated from the chloroform fraction of Amberboa ramosa and the structure was assigned as 4beta-(hydroxymethyl)-3beta,4alpha-dihydroxy-8alpha-[(S)-3-hydroxy-2-ethylenepropionyloxy]-1alphaH, 5alphaH,6betaH,7alphaH,11betaH,11alpha-methylguaia-10(14)-en-6, 12-olide by extensive NMR studies.     

1H and 13C NMR study of 5-substituted-4- (arylidene)amino-2,4-dihydro-3H-1,2,4-triazole-3-thiones and 6-aryl-3-(D-gluco- pentitol-1-yl)-7H-1,2,4-triazolo[3,4-b] [1,3,4]thiadiazines

Five 5-substituted-4-(arylidene)amino-2,4-dihydro-3H-1, 2,4-triazole-3-thiones (2a-2e) and seven 6-aryl-3-(D-gluco-pentitol-1-yl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazines (3a-3g) were synthesized. The complete 1H and 13C NMR chemical shift assignments were analyzed on one- and two-dimensional NMR techniques, including DEPT, NOE-DIF, COSY, gHMBC, and gHSQC.     

A new eremophilanolide from Senecio sinuatus Gilib

From the hexane extracts of Senecio sinuatus roots, the new 3beta-angeloyloxy-6beta-hydroxyeremophil-1(10)-en-8beta,12-olide (3), along with the known compounds 3beta-angeloyloxy-6beta-hydroxyeremophil-1(10)-ene (1), 3beta-senecioyloxy-6beta-hydroxyeremophil-1(10)-ene (2), and 3beta-angeloyloxy-6beta,8alpha-dihydroxyeremophil-1(10)-en-8beta,12-olide (4), were isolated. Complete 1H and 13C NMR chemical shift assignments of 1-4 were achieved using one- and two-dimensional NMR techniques, including gHMQC and gHMBC experiments. A Monte Carlo search, followed by B3LYP/6-31G*DFT calculation, provided the theoretical conformations of the eremophilane rings, which were in agreement with results derived from 1H-1H NMR coupling constant analysis, and confirmed by NOESY experiments.     

Structural determination of flavonoids from Sophora flavescens

Eight flavonoids were isolated from Sophora flavescens. Among them, three prenylflavanones: (2S)-6[2(3-hydroxyisopropyl)-5-methyl-4-hexenyl]-5-methoxy-7,2', 4'-trihydroxyflavanone (1), (2S)-5, 4'-dimethoxy-8-lavandulyl-7, 2'-dihydroxy flavanone (2) and (2S)-8-(5-hydroxy-2-isopropenyl-5-methylhexyl)-7-methoxy-5,2', 4'-trihydroxyflavanone (3) are new compounds. Their chemical structures were determined by spectral methods including 2D NMR.     

A new isocoumarin from Hypericum annulatum

A new isocoumarin, annulatomarin (1), together with the known physcion and beta-sitosterol were isolated from the aerial parts of Hypericum annulatum. The structure of the new compound was established as 6,8-dihydroxy-7-methoxy-3-phenyl-3,4-dihydro-1H-isochromen-1-one on the basis of detailed spectroscopic analysis. Annulatomarin exhibited a modest growth-inhibitory activity in vitro against human chronic myeloid leukaemia LAMA-84 cells with an IC(50) = 111 microM.     

天然产物的绝对构型研究(Ⅰ)——通过比较旋光和碳谱的实验值与计算值确定酮类、内酯类和醇类化合物的绝对构型

在研究天然产物绝对构型的过程中, 筛选了系列绝对构型未鉴定的化合物, 在B3LYP/aug-cc-pVDZ//B3LYP/6-31G(d)水平上计算了它们的旋光和碳谱数据. 结果表明, 计算结果与实验数值十分符合, 从而鉴定出了这些化合物的绝对构型. 另外, 根据计算结果和早期实验报告更正了1个化合物的碳谱化学位移.     

Complete assignments of 1H and 13C NMR spectral data for a novel diterpenoid from Semiaquilegia adoxoides

Semiaquilegoside A (1), a new diterpenoid, was isolated from the roots of Semiaquilegia adoxoides. Its chemical structure was established as 3beta, 11- dihydroxy-12-O-beta-D-glucopyranosyl-8,11,13-abietatrien-6-one through spectroscopic techniques and chemical analysis.     

Complete 1H and 13C NMR assignments of three new polyhydroxylated sterols from the South China Sea gorgonian Subergorgia suberosa

Three new polyhydroxylated sterols, 3beta,6alpha,11,20beta,24-pentahydroxy- 9,11-seco-5alpha-24-ethylcholest-7,28-diene-9-one (1), 3-(1',2'-ethandiol)-24- methylcholest-8(9),22E-diene-3beta,5alpha,6alpha,7alpha,11alpha-pentaol (2), 24-methylcholest-7,22 E-diene-3beta,5alpha,6beta,25-tetraol (3) together with five known sterols, were isolated from the EtOH/CH2Cl2 extract of the South China Sea gorgonian Subergorgia suberosa. The complete assignments of the 1H and 13C NMR chemical shifts for these new compounds were achieved by means of 1D and 2D NMR techniques, including HSQC, HMBC, 1H--1H COSY, and NOESY spectra.     

Ring-chain isomerism in conjugated guanylhydrazones: Experimental and theoretical study

Treatment of 1,3-diaryl-propene-2-one with aminoguanidine under acidic conditions for a short reaction period (1?h) delivers - in accordance with a literature report - the corresponding guanylhydrazones. However, when the reaction time was increased to 12?h, formation of the ring annulated product 4,5-dihydro-1H-pyrazole-1-carboximidamide was observed. This is the first case of ring-chain isomerism in conjugated guanylhydrazones. The acyclic conjugated guanylhydrazone and the corresponding annulated product (4,5-dihydro-1H-pyrazole-1-carboximidamide) could be clearly distinguished by means of UV and NMR spectroscopy. The formation of the ring isomer was further confirmed by single crystal XRD analysis. The time-dependent ¹H NMR study indicated the gradual transformation of the open-chain compound into the cyclic one. The mechanistic insights into the formation of these two products were explored using quantum chemical methods which revealed that the ring isomer is thermodynamically more stable than the open-chain isomer by 6–11?kcal/mol and the barrier for cyclization was found to be 31.37?kcal/mol.     

Ab initio molecular orbital study of energies and conformers of 3,4-dihydro-1,2-dithiin, 3,6-dihydro-1,2-dithiin, 4H-1,3-dithiin,and 2,3-dihydro-1,4-dithiin

Optimized geometries and energies for 3,4-dihydro-1,2-dithiin ( 1 ), 3,6-dihydro-1,2-dithiin ( 2 ), 4H-1,3-dithiin ( 3 ), and 2,3-dihydro-1,4-dithiin ( 4 ) were calculated using ab initio 6-31G* and MP2/6-31G*//6-31G* methods. At the MP2/6-31G*//6-31G* level, the half-chair conformer of 4 is more stable than those of 1 , 2 , and 3 by 2.5, 3.5, and 3.6 kcal/mol, respectively. The half-chair conformers of 1 , 2 , 3 , and 4 are 2.9, 7.1, 2.0, and 5.6 kcal/mol, respectively, more stable than their boat conformers. The calculated half-chair structures of 1 – 4 are compared with the calculated chair conformer of cyclohexane and the half-chair structures for cyclohexene, 3,4-dihydro-1,2-dioxin ( 5 ), 3,6-dihydro-1,2-dioxin ( 6 ), 4H-1,3-dioxin ( 7 ), and 2,3-dihydro-1,4-dioxin ( 8 ). © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1064–1071, 1998     

Reaction of perfluoro-1-ethylindan with SiO2/SbF5 and skeletal transformations of perfluoro-3-ethylindan-1-one under the action of SbF5 and SiO2/SbF5

Perfluoro-1-ethylindan heated with excess of SiO₂ in an SbF₅ medium at 75 °C and then treated with water, gives 4-carboxy-perfluoro-3-methylisochromen-1-one. Perfluoro-3-ethylindan-1-one is converted, under the action of SbF₅ at 70 °C, to perfluoro-2-(but-2-en-2-yl)benzoic acid as a mixture of E- and Z-isomers. When the reaction temperature is raised to 125 °C, a solution of salts of perfluoro-3,4-dimethyl-1H-isochromen-1-yl and perfluoro-4-ethyl-1H-isochromen-1-yl cations is obtained. Increase in the reaction time lowers the content of a salt of the latter cation in the solution. Hydrolysis of the solution of the salts gives perfluoro-3,4-dimethylisochromen-1-one and perfluoro-4-ethylisochromen-1-one.     

1H and 13C NMR assignments and X-ray structures for three monocyclic benzoannelated dilactam polyethers

Three monocyclic polyether dilactams, 17,18-dihydro-5H, 9H-dibenzo[e,n]1,4,10,7,13trioxadiazacyclopentadecine-6,10(7H,11H)-dione (1); 9,10,20,21-tetrahydro-5H, 12H-dibenzo[e,q]1,4,10,13,7,16tetraoxadiazacyclooctadecine-6, 13(7H,14H)-dione (2); and 6,7,9,10-tetrahydro-16H, 20H-dibenzo[h,q]1,4,7,13, 10,16tetraoxadiazacyclooctadecine-17, 21(18H,22H)-dione (3) were isolated during the synthesis of several benzoannelated cryptands. The complete assignments of the 1H and 13C NMR spectra of 1, 2 and 3 in CDCl3 were made using gCOSY, gHMBC, gHMQC, HMQC, HSQC, and NOESY 1D techniques. The ortho (H2) benzene protons show significant downfield shifts (1.16-1.43 ppm) that are consistent with an exodentate orientation for the amide carbonyl groups. The X-ray crystal structures of 1, 2 and 3 show that the carbonyl groups adopt an exodentate conformation in the solid state.     

Synthesis of 5-[2-(Phenoxy)ethyl] Derivatives of 6-Methyluracil, 6-Methyl-2-thioxo-2,3-dihydro-1H-pyrimidin-4-one,and 2-Imino-6-methyl-2,3-dihydro-1H-pyrimidin-4-one

A synthesis of novel derivatives of 6-methyluracil, 6-methyl-2-thioxo-, and 2-imino-6-methyl-2,3-dihydro-1H-pyrimidin-4-one containing a 2-(phenoxy)ethyl substituent at position 5 of the pyrimidine ring has been carried out. It was found that 5-[2-(phenoxy)ethyl] derivatives of 6-methyl-2-thioxo- and 2-imino-6-methyl-2,3-dihydro-1H-pyrimidin-4-one are obtained by the condensation of the corresponding ethyl 3-oxo-2-(2-phenoxyethyl)butanoates with thiourea or guanidine. 6-Methyl-5-[2-(phenoxy)ethyl]uracils can be prepared by treating 6-methyl-5-[2-(phenoxy)ethyl]-2-thioxo-2,3-dihydro-1H-pyrimidin-4-ones with an excess of aqueous monochloroacetic acid solution. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1213–1217, August, 2005.     

Design, synthesis, and cytotoxic activity of Michael acceptors and enol esters in the benzo[b]acronycine series

A series of 2-acyl-6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-ones (4-6) was prepared by treatment of 6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one (3) with an excess of an appropriate acyl chloride in the presence of aluminum chloride. Treatment of (+/-)-cis-1-hydroxy-2-acyloxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-ones (9, 10) or (+/-)-cis-1,2-diacyloxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-ones (2, 11) with hydrochloric acid gave the corresponding 2-acyloxy-6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-ones, exemplified by acetate 7 and butyrate 8. None of the Michael acceptors 4-6 showed significant antiproliferative activity. Enol esters 7 and 8 were markedly cytotoxic toward L1210 leukemia cells, with IC50 values within the same range of magnitude as (+/-)-cis-1,2-diacetoxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one (S23906-1), currently under phase I clinical trials. In contrast with S23906-1, enol esters 7 and 8 were not reactive toward purified DNA.     

A H, C and N NMR spectroscopic and GIAO DFT study of ethyl 5-oxo-2-phenyl-4-(2-phenylhydrazono)-4,5-dihydro-1H-pyrrole-3-carboxylate

¹⁵N-Labelled ethyl 5-oxo-2-phenyl-4-(2-phenylhydrazono)-4,5-dihydro-1H-pyrrole-3-carboxylate was synthesized by azo-coupling of diazotized aniline (using Na¹⁵NO₂ , 99% ¹⁵N) with ethyl 4,5-dihydro-5-oxo-2-phenyl-(1H)-pyrrole-3-carboxylate. The product was formed as a tautomeric hydrazone mixture as confirmed by ¹³C and ¹⁵N chemical shifts, and was obtained as a mixture of E and Z isomers according to ⁿJ(¹⁵N, ¹³C). A comparison of the ¹H NMR data with GIAO DFT calculations enabled determination of the configuration of the carboxy ester group in both isomers.     

Five new bidesmoside triterpenoid saponins from Stauntonia chinensis

Eleven triterpenoid saponins (1-11) were isolated from Stauntonia chinensis DC. (Lardizabalaceae), including five new compounds, yemuoside YM(21-25) (1-3, 6, 7) structures of which were elucidated by chemical methods and a combination of MS, 1D- and 2D- NMR experiments including DEPT, (1)H--(1)H COSY, HSQC, HMBC, TOCSY, and NOESY as 3-O-alpha-L-arabinopyranosyl-(1 --> 3)-[alpha-L-rhamnopyranosyl-(1 --> 2)-]alpha-L-arabinopyranosyl-akebonicacid-28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (1), 3-O-beta-D-xylopyranosyl-(1 --> 3)-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl-akebonic acid-28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (2), 3-O-beta-D-glucopyranosyl-(1 --> 3)-alpha-L-arabinopyranosyl-akebonic acid-28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (3), 3-O-alpha-L-arabinopyranosyl-(1 --> 3)-[alpha-L-rhamnopyranosyl-(1 --> 2)-]alpha-L-arabinopyranosyl-akebonic acid-28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (6), 3-O-alpha-L-arabinopyranosyl-(1 --> 3)-[alpha-L-arabinopyranosyl-(1 --> 2)-]alpha-L-arabinopyranosyl-akebonic acid-28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (7).