Complete NMR Spectral Assignments Research Articles

Structural elucidation and complete NMR spectral assignments of Monascus monacolin analogues.

Three new monacolin analogues, 3,6-dihydroxy-monacolin P (1), 6-methoxy monacolin S (2), and 6-methoxy dehydromonacolin S (3), were isolated from a fraction that strongly inhibited 3-hydroxy-3-methylglutaryl-CoA reductase from the ethyl acetate portion of red yeast rice ethanol extract. Their structures were determined through a combination of 1D and 2D NMR experiments, mass spectrometry analysis, and known literature reports.

Complete 1H and 13C NMR spectral assignment of d-glucofuranose

Although d-glucose is the most common sugar in nature, only a few NMR studies have focused on its minor furanose forms, and they have been limited to the anomeric position. Here, complete 1H and 13C NMR spectral analysis of α- and β-d-glucofuranose was performed, including signal assignment, chemical shifts, and coupling constants. Selective and non-selective 1D and 2D NMR experiments were used for the analysis, complemented by spin simulations and iterative spectral analysis.

α-Actinin-1 promotes activity of the L-type Ca2+ channel Cav 1.2.

The L-type Ca2+ channel CaV 1.2 governs gene expression, cardiac contraction, and neuronal activity. Binding of α-actinin to the IQ motif of CaV 1.2 supports its surface localization and postsynaptic targeting in neurons. We report a bi-functional mechanism that restricts CaV 1.2 activity to its target sites. We solved separate NMR structures of the IQ motif (residues 1,646-1,664) bound to α-actinin-1 and to apo-calmodulin (apoCaM). The CaV 1.2 K1647A and Y1649A mutations, which impair α-actinin-1 but not apoCaM binding, but not the F1658A and K1662E mutations, which impair apoCaM but not α-actinin-1 binding, decreased single-channel open probability, gating charge movement, and its coupling to channel opening. Thus, α-actinin recruits CaV 1.2 to defined surface regions and simultaneously boosts its open probability so that CaV 1.2 is mostly active when appropriately localized.

Synthesis and complete NMR spectral assignments of new benzylamino coumarin derivative

This research involves the reaction of 4-chloro-3-nitrocoumarin and (4-methoxyphenyl)methanamine, whereby a novel coumarin derivative 4-[(4-methoxybenzyl) amino]-3-nitro-2H-chromen-2-one was obtained in good yield. The reaction was carried out in ethyl acetate, in the presence of triethylamine. Also, a detailed spectral analysis of a new coumarin derivative is presented. Resonance assignment was achieved using one( 1H NMR and 13C NMR) and two-dimensional NMR techniques (1H1H-COSY, NOESY, HSQC, and HMBC). The NOESY correlations of protons from arylamino substituent and coumarin core indicate their spatial orientation.

Enzymatic Synthesis and Structural Characterization of Rebaudioside D3, a Minor Steviol Glycoside of <i>Stevia rebaudiana</i> Bertoni

Rebaudioside D3, a novel steviol glycoside, is produced by specific UDP-glycosyltransferase of rebaudioside E, a minor steviol glycoside of Stevia rebaudiana Bertoni. The complete proton and carbon NMR spectral assignments of rebaudioside D3, 13-[(2-O-β-D-glucopyranosyl-6-O-β-D-glucopyranosyl-β-D-glucopyranosyl) oxy] ent-kaur-16-en-19-oic acid-(2-O-β-D-glucopyranosyl-β-D-glucopyranosyl) ester, was achieved by the extensive 1D and 2D NMR (1H and 13C, TOCSY, HMQC, HMBC) as well as mass spectral data. Further, hydrolysis studies were performed on rebaudioside D3 using acid and enzymatic studies to identify aglycone and sugar residues in its structure. Rebaudioside D3 is detected in the commercial extract of the leaves of Stevia rebaudiana by LC-MS analysis, suggesting rebaudioside D3 is a natural steviol glycoside.

NMR Spectral Analysis and Hydrolysis Studies of Rebaudioside N, a Minor Steviol Glycoside of <i>Stevia rebaudiana</i> Bertoni

The complete proton and carbon NMR spectral assignments of a diterpene glycoside isolated from the commercial extract of the leaves of Stevia rebaudiana Bertoni, 13-[(2-O-β-D-glucopyranosyl-3-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy] entkaur-16-en-19-oic acid-[(2-O-α-L-rhamnopyranosyl-3-O-β-D-glucopyranosyl-β-D-glucopyranosyl) ester] (1); also known as rebaudioside N, was achieved by the extensive 1D and 2D NMR (1H and 13C, COSY, HMQC, HMBC) as well as mass spectral data. Further, hydrolysis studies were performed on rebaudioside N using acid and enzymatic studies to identify aglycone and sugar residues in its structure.

Structure elucidation and complete NMR spectral assignments of glucosylated saponins of cantalasaponin I

Five new glucosylated steroidal glycosides, cantalasaponin I-B(1) (1), I-B(2) (2), I-B(3) (3), I-B(4) (4) and I-B(5) (5), were isolated and purified from the transformed product of the cantalasaponin I by using Toruzyme 3.0 l as biocatalyst. Their structures were elucidated on the basis of high-resolution electrospray ionization mass spectrometry, one-dimensional ((1) H and (13) C NMR) and two-dimensional [COSY, heteronuclear single-quantum correlation (HSQC), HMBC and HSQC-TOCSY] NMR spectral analyses and chemical evidence.

Complete NMR spectral assignments of two lactucin‐type sesquiterpene lactone glycosides from Picris conyzoides

Complete (1)H and (13)C NMR signal assignments of two lactucin-type sesquiterpene lactone glycosides, derivatives of 11β,13-dihydrolactucin, isolated from roots of Picris conyzoides, were achieved by one- and two-dimensional NMR experiments, allowing the correction of previously published data for cichorioside B and the structure elucidation of its new ester with 3-hydroxy-2-methylpropanoic acid. In addition, seven known sesquiterpene lactones and three phenolic compounds were isolated from the plant material.

Minor diterpenoid glycosides from the leaves of Stevia rebaudiana

From the commercial extract of the leaves of Stevia rebaudiana, three new diterpenoid glycosides were isolated besides eight known steviol glycosides including stevioside, rebaudiosides A–F and dulcoside A. The structures of the three compounds were identified as 13-[(2- O-β- d-glucopyranosyl-β- d-glucopyranosyl) oxy]-kaur-16-en-18-oic acid-(6- O-β- d-xylopyranosyl-β- d-glucopyranosyl) ester ( 1), 13-[(2- O-β- d-glucopyranosyl-β- d-glucopyranosyl) oxy]-17-hydroxy-kaur-15-en-18-oic acid β- d-glucopyranosyl ester ( 2), and 13-[(2- O-β- d-glucopyranosyl-β- d-glucopyranosyl) oxy]-17-oxo-kaur-15-en-18-oic acid β- d-glucopyranosyl ester ( 3) on the basis of extensive NMR and MS spectral studies. Another known diterpenoid glycoside, 13-[(2- O-β- d-glucopyranosyl-β- d-glucopyranosyl) oxy]-kaur-15-en-18-oic acid β- d-glucopyranosyl ester ( 4) was also isolated and its complete NMR spectral assignments were made on the basis of COSY, HSQC and HMBC spectral data.

Cucurbitane Glycosides from Siraitia grosvenorii

Systematic phytochemical studies of the extract of Luo Han Go (Siraitia grosvenorii) furnished six known cucurbitane glycosides, namely, mogrosides IVa, mogrosides V and VI, isomogroside V, 11-oxomogroside V, and siamenoside I. The structures of all the isolated compounds were characterized on the basis of extensive spectral and chemical studies. Though the partial NMR spectral data has been reported for some of the isolated compounds previously, the complete 1H and 13C NMR spectral assignments of all the isolated compounds are reported herewith for the first time based on COSY, HSQC, HMBC, and NOESY spectroscopic data.

ChemInform Abstract: The Synthesis and Complete 1H and 13C NMR Spectral Assignment of 2,2,4,4,6,6-Hexanitroadamantane and Its Precursor Nitroketones by 2D NMR Spectroscopy.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis, complete NMR spectral assignments, and antifungal screening of new 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one oxime derivatives

A series of differently substituted 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one oximes have been synthesized and their 1H and 13C NMR chemical shifts have been unambiguously assigned using H,H-COSY, NOESY, HSQC, and HMBC spectral data. On the basis of the NMR studies, irrespective of the nature and position of the substituents, all reported compounds exist in twin-chair conformation with equatorial disposition of the phenyl groups at C-2 and C-4 of the 3-azabicyclononane moiety. Among the synthesized oxime derivatives, compounds with halo-substituents at ortho/para positions of the phenyl showed good antifungal profile against all tested organisms.

Synthesis and properties of 1-(3-(fluoromethyl and trifluoromethyl)phenyl)-5-oxopyrrolidine-3-carboxylic acid derivatives

Condensation of 1-(3-(fluoromethyl and trifluoromethyl)phenyl)-5-oxopyrrolidine-3-carbohydrazides with aromatic aldehydes and acetone gave the corresponding hydrazones. Most of the reaction products are able to form isomers, because of the amide and azomethine structural units. The reactions of 1-aryl-4-hydrazinocarbonyl-2-pyrrolidinones with 2,4-pentanedione gave 3,5-dimethylpyrazole compounds and those with 2,5-hexanedione provided 1-substituted 2,5-dimethylpyrroles. Several oxadiazole derivatives were synthesized. The structures of the synthesized compounds were confirmed on the basis of their MS, IR, 1H, and 13C NMR spectra and by analytical methods. 13C APT, 1H/13C 2D (HETCOR), and NOE (1H) NMR techniques and molecular modeling were used for detailed structure examination. Complete NMR spectral assignment of the studied compounds was performed in order to evaluate their conformation, configuration, and substituent effects.

Structure elucidation and complete NMR spectral assignment of two triterpenoid saponins from Radix Hedysari

A new oleanane-type triterpenoid saponin with a carbonyl group at C-15, named polybosaponin A (1), together with a known triterpenoid saponin, dehydrosoyasaponin I (2), were isolated from Radix Hedysari. On the basis of one- and two-dimensional NMR and high resolution electrospray ionization mass spectrometry, the structure of 1 were elucidated and the (1)H and (13)C NMR spectral signals were assigned totally. In addition, the complete assignment of (1)H NMR signals and revision of incorrect assignment of (13)C NMR signals for 2 were also achieved based on one- and two-dimensional NMR spectrometry.

Structure elucidation and complete NMR spectral assignments of two new sesquiterpene lactone xylosides from Lactuca triangulata.

Two new sesquiterpene lactone xylosides, derivatives of the guaianolides 9alpha-hydroxyleucodin and 9alpha-hydroxy-11,13-dehydroleucodin, were isolated from roots of Lactuca triangulata. Their structures were established on the basis of (1)H and (13)C NMR spectra, 2D NMR (HMQC, HMBC, COSY, NOESY) techniques and comparison with the literature data. The compounds represent the first example of sesquiterpene lactone xylosides.

Structure elucidation and complete NMR spectral assignments of two new dammarane‐type tetraglycosides from Panax quinquefolium

Two new saponins were isolated from leaves of Panax quinquefolium and their structures were elucidated as 3beta, 12beta, 20S-trihydroxy-25-methoxydammar-23-ene 3-O-{[beta-D-glucopyranosyl(1-->2)-beta-D-glucopyranosyl]-20-O-[alpha-L-arabinopyranosyl(1-->6)]-beta-D-glucopyranoside (1) and 3beta, 20S-dihydroxy-12beta, 23R-epoxydammar-24-ene 3-O-{[beta-D-glucopyranosyl(1-->2)-beta-D-glucopyranosyl]-20-O-[beta-D-xylopyanosyl(1-->6)]-beta-D-glucopyranoside (2) on the basis of (1)D and (2)D NMR (including (1)H, (13)C-NMR, (1)H-(1)H COSY, HSQC, TOCSY, HMBC, and NOESY), ESI-MS spectrometry and chemical methods.

Substituent effects of the N,N‐dimethyl‐ sulfamoyl group on the 1H and 13C NMR spectra of positional isomers of quinolines

The complete 1H and 13C NMR spectral assignments of seven positional isomers of N,N-dimethylsulfamoylquinolines 2-8 and quinoline have been made using 1D and 2D NMR techniques, including COSY, HMQC and HMBC experiments. Deltadelta(H) and Deltadelta(C) substituent effects induced by the sulfamoyl group were determined. The sulfamoyl substituent affects proton and carbon chemical shifts both in the parent and in the fused (pyridine or benzene) ring.

Complete NMR spectral assignments of siloxanol based copolycarbonate including the configurational copolymer structure and the determination of each monomer conversion

Siloxanol based copolycarbonate(SicoPC) of which the constitutional monomers are diphenyl carbonate, bisphenol A, and polydimethylsiloxanol(PDMS), was prepared by melt transesterification polymerization. The objective was to investigate the monomer conversion ratio for each monomer and the configurational structure of the SicoPC. A laboratory scale 5L reactor was used in the siloxanol preparation where the reactor jacket oil temperature was kept constant at 230 °C throughout the first and second polymerization phases. The reaction pressure was varied. For the first phase, the pressure was dropped from the atmospheric pressure 1000–200 mbar during the target reaction time of 30 min to remove the byproduct phenol. The second phase, the full vacuum pressure of was maintained for the second 30-min polymerization phase. An hour of reaction under such a condition gave a product of a highly viscous melt, of which the number average molecular weight read approximately 3000 g/mol. Complete NMR spectral assignments of the obtained melt (expected to be SicoPC) were made using both 1H and 13C, followed by 2D NMR spectroscopy. The measurements confirmed that the obtained melt was indeed the expected SicoPC; the conversion ratio of each monomer, BPA, DPC and PDMS were 100%, 99.5% and 86%, respectively. Furthermore, the HMBC (heteronuclear multiple quantum coherence) experiment confirmed the most important fact in determining the configurational structure of a SicoPC – all the PDMS monomers were located at the end chain of SicoPC.

Separation of floridoside and isofloridosides by HPLC and complete 1H and 13C NMR spectral assignments for d-isofloridoside

Isofloridosides (1- O-α- d-galactopyranosylglycerol) and floridoside (2- O-α- d-galactopyranosylglycerol) were extracted from the red alga Porphyra umbilicalis (Linné) Kützing (Bangiales, Rhodophyta). Their separation was achieved by HPLC (NH 2 P50 column) after successive purification of the crude extract by ion-exchange chromatography and HPLC (Sugar-Pak TM1 column). 1D and 2D NMR spectroscopy experiments allowed to completely assign the 1H and 13C spectra of d-isofloridoside.

Structure elucidation and complete NMR spectral assignments of three new lanostanoid triterpenes with unprecedented Δ16, 17 double bond from Ganoderma lucidum

Three new lanostanoid triterpenes named 3beta,7beta-di- hydroxy-11,15,23-trioxo-lanost-8,16-dien-26-oic acid (1), 3beta,7beta-dihydroxy-11,15,23-trioxo-lanost-8,16-dien-26-oic acid methyl ester (2), and 12beta-acetoxy-3beta,7beta-dihydroxy-11,15,23-trioxo-lanost-8,16-dien-26-oic acid (3) were isolated from the fruit bodies of Ganoderma lucidum. They all show a Delta(16, 17) double bond unprecedented in such types of lanostanoid triterpenes possessing the side chain at C-17. The complete NMR assignments for these compounds were carried out using (1)H, (13)C, DEPT, COSY, HSQC, HMBC, and ROESY NMR experiments.