Spectral study of a new dihydroisocoumarin

A novel dihydroisocoumarin, 3,4‐dihydro‐6,8‐dihydroxy‐3‐(2′‐acetyl‐3′‐hydroxy‐5′‐methoxy)methyl‐1H‐[2]benzopyran‐1‐one, was isolated from the chloroform extract of the sap of the traditional herb Aloe vera. Its structure was determined by high‐resolution negative fast atom bombardment mass spectrometry (MS), 2D NMR spectroscopy and x‐ray crystallography. The molecular structure was elucidated by 2D NMR analysis. The complete assignment of the ¹H and ¹³C NMR spectra of this compound was performed by using ¹H detected one‐bond heteronuclear multiple quantum correlation (HMQC) and long‐range (two and three bonds) heteronuclear multiple quantum bond correlation (HMBC) experiments. Detailed analyses of the one‐ and two‐dimensional NMR techniques are presented in additional to the spectral properties (MS, IR and UV). Copyright © 2003 John Wiley & Sons, Ltd.     

A new rosane-type diterpenoid from Stachys parviflora and its density functional theory studies

A new rosane-type diterpenoid (1) has been isolated from the chloroform fraction of Stachys parviflora. Structure of 1 was proposed based on 1D and 2D NMR techniques including correlation spectroscopy, heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation and nuclear Overhauser effect spectroscopy. A theoretical model for the electronic and spectroscopic properties of compound 1 is also developed. The geometries and electronic properties were modelled at B3LYP/6-31G^* and the theoretical scaled spectroscopic data correlate nicely with the experimental data.     

Advanced solvent signal suppression for the acquisition of 1D and 2D NMR spectra of Scotch Whisky

A simple and robust solvent suppression technique that enables acquisition of high‐quality 1D ¹H nuclear magnetic resonance (NMR) spectra of alcoholic beverages on cryoprobe instruments was developed and applied to acquire NMR spectra of Scotch Whisky. The method uses 3 channels to suppress signals of water and ethanol, including those of ¹³C satellites of ethanol. It is executed in automation allowing high throughput investigations of alcoholic beverages. On the basis of the well‐established 1D nuclear Overhauser spectroscopy (NOESY) solvent suppression technique, this method suppresses the solvent at the beginning of the pulse sequence, producing pure phase signals minimally affected by the relaxation. The developed solvent suppression procedure was integrated into several homocorrelated and heterocorrelated 2D NMR experiments, including 2D correlation spectroscopy (COSY), 2D total correlation spectroscopy (TOCSY), 2D band‐selective TOCSY, 2D J‐resolved spectroscopy, 2D ¹H, ¹³C heteronuclear single‐quantum correlation spectroscopy (HSQC), 2D ¹H, ¹³C HSQC‐TOCSY, and 2D ¹H, ¹³C heteronuclear multiple‐bond correlation spectroscopy (HMBC). A 1D chemical‐shift‐selective TOCSY experiments was also modified. The wealth of information obtained by these experiments will assist in NMR structure elucidation of Scotch Whisky congeners and generally the composition of alcoholic beverages at the molecular level.     

New sesquiterpenes from Euonymus europaeus (Celastraceae)

A new sesquiterpene evoninate alkaloid (1), and two sesquiterpenes (2, 3) with a dihydro-beta-agarofuran skeleton, along with three known sesquiterpenes (4-6), were isolated from the seeds of Euonymus europaeus. Their structures were elucidated by high resolution mass analysis, and one- and two-dimensional (1D and 2D) NMR spectroscopy, including homonuclear and heteronuclear correlation [correlation spectroscopy (COSY), rotating frame Overhauser enhancement spectroscopy (ROESY), heteronuclear single quantum coherence (HSQC), and heteronuclear multiple bond correlation (HMBC)] experiments.     

NMR study on 9‐S and 9‐R oxirane derivatives of ascomycin

Structure elucidation of 9‐S and 9‐R oxirane derivatives of ascomycin, a 23‐membered immunomodulating macrolactam, was performed using NMR spectroscopy. The total ¹H and ¹³C signal assignments required the gradient‐selected versions of COSY (gs‐COSY), heteronuclear multiple quantum‐correlation spectroscopy (gs‐HSQC), heteronuclear multiple‐bond correlation spectroscopy (gs‐HMBC), and nuclear Overhauser methods. The data sets then were used to examine the dependence of ketone–hemiketal and cis–trans amide equilibria on the substitution pattern and the absolute configuration of the chiral oxirane. Copyright © 2002 John Wiley & Sons, Ltd.     

First natural urease inhibitor from Euphorbia decipiens

Three new diterpene esters with a myrsinol-type skeleton have been isolated from Euphorbia decipiens BOISS. & BUHSE. The structure elucidation of the isolated compounds was based primarily on two-dimensional (2D)-NMR techniques including correlation spectroscopy (COSY), heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC) and nuclear Overhauser effect spectroscopy (NOESY) experiments. Compounds 1 and 3 are active against prolyl endopeptidase and compound 2 showed inhibitory activity against urease enzyme.     

NMR studies on 1,2‐dihydro‐2‐(4‐aminophenyl)‐4‐[4‐(4‐aminophenoxy)‐4‐phenyl]‐(2H)phthalazin‐1‐one

An unsymmetrical heterocyclic diamine, 1,2‐dihydro‐2‐(4‐aminophenyl)‐4‐[4‐(4‐aminophenoxy)‐4‐phenyl]‐(2H)phthalazin‐1‐one, was synthesized. Its ¹H and ¹³C NMR spectra were completely assigned by utilizing the two‐dimensional heteronuclear ¹³C–¹H multiple‐bond coherence (HMBC) spectroscopy, and heteronuclear ¹³C–¹H one‐bond correlation spectroscopy, homonuclear shift correlation spectroscopy (H,H‐COSY) and rotating frame Overhauser enhancement spectroscopy (ROESY). The structure of the compound was shown to be the phthalazinone rather than the phthalazine ether from cross peaks and chemical shifts of the protons. Copyright © 2002 John Wiley & Sons, Ltd.     

Structural determination of quercusides A and B,new flavonoid glucosides from Quercus incana,by 1D and 2D NMR spectroscopy

Quercusides A and B, new flavonoid glucosides have been isolated from the chloroform soluble fractions of Quercus incana. Their structures were assigned from ¹H and ¹³C nuclear magnetic resonance spectra, distortionless enhancement by polarization transfer (DEPT) and by correlation spectroscopy, heteronuclear multiple quantum correlation (HMQC) and heteronuclear multiple bond correlation (HMBC) experiments. Lupeol, β‐sitosterol and ursolic acid have also been reported from this species. Copyright © 2009 John Wiley & Sons, Ltd.     

Isolation and characterisation of three new anthraquinone secondary metabolites from Symplocos racemosa

Three new anthraquinone secondary metabolites were isolated from Symplocos racemosa, a small tree of family symplocaceae. The structures of compounds (1–3) were elucidated to be 1,4-dihydroxy-6-(ethoxymethyl)-8-propylanthracene-9,10-dione (1), 1,4-dihydroxy-6-(hydroxymethyl)-8-butylanthracene-9,10-dione (2) and 1,4-dihydroxy-6-(hydroxymethyl)-8-propyl anthracene-9,10-dione (3) using their spectral data, i.e. through IR, UV, ¹H NMR, ¹³C NMR and two-dimensional (2D) NMR techniques including heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation and correlation spectroscopy.     

Two new 5-deoxyflavones from Albizia odoratissima

Two new 5-deoxyflavones, 7,8-dimethoxy-3',4'-methylenedioxyflavone (1) and 7,2',4'-trimethoxyflavone (2) together with a known flavone, 7,4'-dimethoxy-3'-hydroxyflavone (3) were isolated from the rootbark of Albizia odoratissima. The structures of these new compounds were elucidated by electrospray ionization mass spectrometry (ESI-MS) and 1D and 2D-NMR spectral studies including (1)H-(1)H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY).     

New taxane diterpenoids from Taiwanese Taxus sumatrana

Two new taxane diterpenoids, tasumatrols A (1) and B (2), have been isolated from extracts of the leaves and twigs of Taiwanese Taxus sumatrana. Tasumatrol A is a rare 5/6/6 taxene system, having a novel gamma-lactone at C-10 and C-19. The structures of compounds 1 and 2 were determined on the basis of two dimensional (2D)-NMR techniques, including correlation spectroscopy (COSY), 1H-detected heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond connectivity (HMBC) experiments.     

Waterborne polyesters partially based on renewable resources

A new experimental approach for preparing biobased, water‐soluble polyesters (PEs) via titanium(IV) n‐butoxide‐catalyzed bulk polycondensation is presented. In the described method polymers were obtained from isosorbide, maleic anhydride and poly(ethylene glycol) (PEG). The chemical structure of the synthesized PEs was confirmed using 2D NMR spectroscopy and by titration methods. Careful analysis of 2D NMR spectra viz. correlation spectra (COSY), heteronuclear single quantum correlation spectra (HSQC) and heteronuclear multiple‐bond correlation spectra (HMBC) allowed to accomplish the complete proton assignment of isosorbide, PEG, and unsaturated acid residues in the PEs. Moreover, by using NMR spectroscopy the transformation of maleic anhydride into fumaric acid ester and the absence of maleic acid ester units in the final polymer were proven. However, during polycondensation part of the unsaturated bonds has reacted in a Michael addition with isosorbide or PEG. Gel permeation chromatography measurements revealed that the unsaturated PEs have M_n values in the range 3000–5000 g/mol. These PEs, with a low content of carboxylic acid end groups, exhibited sufficient thermal resistance for practical applications, for example, as free radical curable coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Two new 5-deoxyflavonoids from Calliandra inermis

Two new 5-deoxyflavonoids, 7,2',3',4'-tetramethoxyflavone (1) and 7,2',3',4'-tetramethoxyflavanone (2) together with a known flavone 7,4'-dimethoxy-3'-hydroxyflavone (3) were isolated from the whole plant of Calliandra inermis. The structures of these new compounds were elucidated by high resolution electron impact mass spectrometry (HR-EI-MS) and 1D and 2D-NMR spectral studies including 1H-1H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY).     

Simple and Efficient Synthesis of Novel 3‐Substituted 2‐Thioxo‐2,3‐dihydro‐1H‐benzo[g]quinazolin‐4‐ones and Their Reactions with Alkyl Halides and α‐Glycopyranosyl Bromides

A series of 3‐substituted 2‐thioxo‐2,3‐dihydro‐1H‐benzo[g]quinazolin‐4‐ones 4a – e were synthesized from the reaction of 3‐aminonaphthalene‐2‐carboxylic acid 1 with isothiocyanate derivatives 2a – e . The alkylation of 4a – e with alkyl halides gave 3‐substituted 2‐alkylsulfanyl‐2,3‐dihydro‐1H‐benzo[g]quinazolin‐4‐ones 5a – o . S‐Glycosylation was carried out via the reaction of 4a – e with glycopyranosyl bromides 7a and 7b under anhydrous alkaline conditions. The structure of the compounds was established as S‐nucleoside and not N‐nucleoside. Conformational analysis has been studied by homonuclear and heteronuclear two‐dimensional NMR methods (2D DFQ‐COSY, heteronuclear multiple quantum coherence, and heteronuclear multiple bond correlation). The S site of alkylation and glycosylation was determined from the ¹H and ¹³C heteronuclear multiple quantum coherence experiments.     

New taxane diterpenoids from the roots of Taiwanese Taxus mairei

Five new taxane diterpenoids, taxumairols G (1), H (2), I (3), J (4), and L (5) were isolated from extracts of the roots of Taiwanese Taxus mairei (LEMEE & LEVL.) S. Y. Hu. Compounds 1-4 belong to the new 11(15-->1)-abeo-taxene system, having a tetrahydrofuran ring along carbons C-2, C-3, C-4 and C-20. Compounds 3 and 4 contain an isopropenyl group at C-1 while compounds 1 and 2 are attached with a benzoxyl group at C-15. The structures of compounds 1-5 were determined on the basis of two-dimensional (2D)-NMR techniques including correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond correlation (HMBC), and nuclear Overhauser effect spectroscopy (NOESY) experiments.     

Two new pentacyclic triterpenoids from Lantana camara LINN

Two new pentacyclic triterpenoids, namely lantanoic acid (1) and camaranoic acid (2), and six known compounds such as lantic acid, camarinic acid, camangeloyl acid, camarinin, oleanonic acid, and ursonic acid were isolated from the aerial parts of Lantana camara LINN. Structures of the new constituents were elucidated by chemical transformation and spectral studies including 1D ((1)H- and (13)C-NMR) and 2D ((1)H-(1)H correlation spectroscopy (COSY), nuclear Overhauser effect spectroscopy (NOESY), (1)H-(1)H total correlation spectroscopy (TOCSY), J-resolved, (1)H-detected heteronuclear multiple quantum coherence (HMQC), and heteronuclear multiple bond connectivity (HMBC)) NMR spectroscopy.     

Two new 2'-oxygenated flavones from Andrographis elongata.

Two new 2'-oxygenated flavones, 5,2',6'-trihydroxy-7-methoxyflavone (3) and skullcapflavone I 2'-O-beta-D-(4"-E-cinnamyl) glucopyranoside (5), together with three known flavones, 7-O-methylwogonin (1), skullcapflavone I (2) and skullcapflavone I 2'-O-beta-D-glucopyranoside (4) were isolated from the whole plant of Andrographis elongata, and the structures were elucidated by FAB-MS and one- and two-dimensional (1D- and 2D)-NMR spectral studies including 1H-1H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and rotating frame Overhauser enhancement spectroscopy (ROESY) experiments, and chemical studies.     

The complete 1H and 13C chemical shift assignments of a cyclopropylpyrroloindole analog: Adozelesin

The ¹H and ¹³C nmr spectral assignments of [7bR]-N-[2-[(4,5,8,8a-tetrahydro-7-methyl-4-oxocyclo-propa[c]pyrrolo[3,2-e]indol-2(1H)-ylcarbonyl]-1H-indol-5-yl]-2-benzofurancarboxamide (Adozelesin) (1) are described. Complete and unambiguous assignments of the hydrogen and carbon spectra were made using a combination of conventional homonuclear and gradient-selected inverse-detected heteronuclear nmr experiments: double quantum filtered ¹H-¹H correlation spectroscopy (COSY), gradient-selected heteronuclear single quantum coherence spectroscopy (gs-HSQC), and gradient-selected heteronuclear multiple bond coherence spectroscopy (gs-HMBC). The enhanced sensitivity of these experiments allowed a smaller sample concentration and shorter spectral collection times for a full nmr analysis of this compound. The nmr data corroborates the published structure of this compound.     

Two new diterpenoids from Ballota limbata

Two new clerodane-type diterpenoids trivially named as ballotenic acid (1) and ballodiolic acid (2) have been isolated from Ballota limbata along with three the known compounds; beta-amyrin, oleanolic acid, and beta-sitosterol. The structure elucidation of the new compounds was based primarily on two-dimensional (2D)-NMR techniques including correlation spectroscopy (COSY), heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC), and nuclear Overhauser effect (NOE) experiments. Compounds 1 and 2 displayed inhibitory potential against lipoxygenase enzyme in a concentration-dependent fashion with IC(50) values of 99.6 microM and 38.3 microM, respectively.     

A new chalcone and a flavone from Andrographis neesiana

Two new flavonoids, 2',4',6',2,3,4-hexamethoxychalcone (1) and 5-hydroxy-7,2',5'-trimethoxyflavone (2) together with a known flavone glycoside, echioidinin 5-O-beta-D-glucopyranoside (3) were isolated from the whole plant of Andrographis neesiana, and the structures were elucidated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and one- and two-dimensional (1D- and 2D)-NMR spectral studies including 1H-1H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY) experiments.