Scalar coupling patterns contain a wealth of structural information. The determination, especially of small scalar coupling constants, is often prevented by merging the splittings with the signal line width. Here we show that real-time J-upscaling enables the visualization of unresolved coupling constants in the acquisition dimension of one-dimensional (1D) or multidimensional NMR spectra. This...

Theoretical and experimental aspects of T,, are discussed for a heteronuclear HX twospin system (T$) where only the X nucleus is spin-locked. An expression for TE in terms of spectral density functions and the effective magnetic field parameters is developed. It shows that T:, offers potentially dierent information about the spectral densities than either r:, TF, or the steady-state NOEX. We pr...

A new sesquilignan glycoside 1, together with seven known phenolic glycosides 2-8 were isolated from the aerial parts of Capsella bursa-pastoris. The chemical structure of the new compound 1 was elucidated by extensive nuclear magnetic resonance (NMR) data (¹H- and 13C-NMR, ¹H-¹H correlation spectroscopy (¹H-¹H COSY), heteronuclear single-quantum correlation (HSQC), heteronuclear multiple bond ...

The principles of molecular geometry determination by high-quantum heteronuclear local field spectroscopy in solid-state NMR are discussed. The extreme multiple-quantum coherences in a cluster of nuclear spins are allowed to evolve in the presence of heteronuclear through-space couplings to two spins of a different type. The multiple-quantum dephasing curve is independent of the homonuclear spi...

Ginseng roots were extracted with aqueous methanol, and extracts were suspended in water and extracted successively with ethyl acetate and n-butanol. Column chromatography using the n-butanol fraction yielded four purified triol ginseng saponins: the ginsenosides Re, Rf, Rg2, and 20-gluco-Rf. The physicochemical, spectroscopic, and chromatographic characteristics of the ginsenosides were measur...

The isolation and characterization of three new oleanane-type triterpenoidal saponins, called gleditsiosides E-G, along with two known ones, from the anomalous fruits of Gleditsia sinensis LAM. are described. Their structural details were unambiguously determined by using a combination of modern NMR techniques, including distortionless enhancement by polarization transfer (DEPT), double-quantum...

A method is described for measurement of small unresolvable heteronuclear J couplings. The method is based on quantitative analysis of a phase-purged heteronuclear spin-echo difference spectrum, and is demonstrated for measuring ~H -~t3Cd and I H-199Hg J couplings in metaJ-substituted rubredoxin (M, ~ 5.4 kDa) from Pyrococcusfuriosus. Couplings from cadmium to backbone amide protons that are hy...

A long-chain alkene (1-hexacosene) and a terpene were obtained from the bioactive methanol extract of the air-dried leaves of Pipturus arborescens (Link) C.B. Rob (“Handalamay”) collected from Poblacion, Kapatagan, Lanao del Norte. The compounds were isolated through extraction with ethanol, sequential partitioning with water-chloroform and hexane-90% methanol followed by fractionation and puri...

Two new triterpenoid saponins (1, 2) were isolated from the roots of Gypsophila altissima L. (Caryophyllaceae), together with a known compound (3). The structures of new saponins were established as quillaic acid 3-O-beta-D-xylopyranosyl-(1-->3)-beta-D-glucuronopyranoside (1), and 3-O-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta-D-glucuronopyranosyl quillaic acid 28-O-(6-...

A rotary resonance echo double resonance (R-REDOR) experiment is described for measuring heteronuclear dipolar coupling under magic-angle spinning. Rotary resonance reintroduces both dipolar coupling and chemical shift anisotropy with an rf field matching the spinning frequency. The resonance effect from chemical shift anisotropy can be refocused with a rotary resonance echo. The R-REDOR experi...