In our screening of marine Streptomycetes for bioactive compounds, in addition to the known metabolites rabelomycin (1), fridamycin D (2b), N-benzylacetamide and N-(2'-phenylethyl)acetamide, two new anthracycline antibiotics designated as himalomycin A (2c) and B (2d) were isolated from the culture broth of the marine Streptomyces sp. isolate B6921. The structure of the new antibiotics was dete...

A novel approach to the determination of structure and potential dynamics in the solid-state NMR spectroscopy of half-integer quadrupolar nuclei is proposed and demonstrated. The new experiment combines into a single three-dimensional sequence, 2D multiple-quantum magic-angle-spinning NMR and 2D exchange NMR protocols. The result separates for each inequivalent chemical site its spin-diffusion ...

A recently proposed protocol enables the acquisition of two-dimensional nuclear magnetic resonance (2D NMR) spectra within a single scan. A promising application opened up by this new data acquisition mode concerns its combination with active nuclear polarization methods, whereby spectroscopy is carried out on analytes whose spin magnetizations have been significantly enhanced over their Boltzm...

The ethyl acetate partition of dried methanolic extract of aerial parts of Euphorbia microsciadia (Euphorbiaceae) afforded three pentacyclic triterpenes, betulinic acid (1) from lupane type, oleanolic acid (2) from oleane type and ursolic acid (3) from ursane type triterpenes that are reported for the first time in this plant. These three compounds were structurally compared through their mass ...

Natural products provide excellent potential leads for drug development because of their chemical diversity and biological functionality. However, the productivity of discovery of new, pharmacologically active natural products has traditionally been low due to inherent difficulties and costs associated with extract dereplication, i.e., isolation, purification and structure elucidation of indivi...

A pillar[5]arene-based [1]rotaxane was simply prepared in a high yield of 73%. Its stucture was confirmed by (1)H NMR, 2D NMR spectra, mass spectra and theoretical calculation.

The 1H and 13C NMR spectra of the neo-clerodane diterpenoid scutecyprin were completely assigned by using a combination of 2D NMR experiments, which included 1H-1H COSY, HSQC, HMBC and NOESY sequences.

We developed several novel two-dimensional (2D) NMR core analysis techniques, which not only enhance the analysis of fluid-saturated rock samples, but also open up an unexplored area for petrophysical research. This is different from the conventional one-dimensional (1D) NMR core analysis, in which only the proton population versus relaxation times, i.e., T1,2 distribution, is displayed to char...

From the stem bark hexanic extract of Garcinia chapelieri, chapexanthone A, B were isolated using combinations of column and thin-layer chromatographic methods. Their structures were elucidated by NMR spectroscopic methods, mainly 1D and 2D NMR.