Assignments were made using the HMQC
, HMBC, COSY, and NOESY spectra.
The structures of isolated compounds were elucidated based on 1-dimensional ([sup.1]H and [sup.13]C NMR) and 2-dimensional NMR (HMQC
and HMBC) spectral data, by comparing with published spectral data, electronic impact (EI), and fast atom bombardment (FAB) mass spectrometry (MS) data.
As the range of the coupling constants is an order of magnitude larger, the ID experiments run to detect the ~145 Hz are called the HSQC or HMQC
. The ID experiment for the smaller, 5-15 Hz coupling is the HMBC.
These compounds were identified by comparing [sup.1]H and [sup.13]C NMR spectra and correlation NMR spectra such as COSY, HMBC, and HMQC
with previously reported data and EI-, FAB-, and MALDITOF MS.
El espectro HMQC
permitio asignar todos los protones a sus correspondientes carbonos y el espectro HMBC permitio correlacionar por ejemplo el carbonilo C-19 a tres enlaces con los protones del metilo C-18, asi como el carbono C-21 con los protones del metilo C-22, ambos enlazados al atomo de azufre.
13C experiments include spectral editing with DEPT, 2-D direct HETCOR experiments and 2-D indirect experiments, such as HSQC, HMQC
[sup.13]C experiments include spectral editing with DEPT, 2-D direct HETCOR experiments and 2-D indirect experiments such as HMQC
Abbreviations BAIB Bis-acetoxy Iodo Benzene Cbz Carboxybezyloxy COSY Correlation Spectroscopy DCM Dichloromethane DMAP Dimethoxy Amino Pyridine DMT Dimethoxytrityl DNA Deoxyribo Nucleic Acid ESI-MS Electrospray Ionization Mass Spectrometry HMQC
Heteronuclear Multiple Quantum Coherence KBr Potassium Bromide MeCN Acetonitrile NMR Nuclear Magnetic Resonance RNA Ribonucleic Acid TEMPO (2,2,6,6-tetramethylpiperidin-l-yl)oxidanyl
Elucidation of the structures of residual and dissolved pine kraft lignins using an HMQC
The structure of compound 1 was further elucidated by examination of its 1D [sup.13]C (75 MHz), DEPT (90[degrees] and 135[degrees]), and [sup.1]H (300 MHz) NMR spectra and HMQC
, HMBC, COSY, and NOESY spectra in MeOH-[d.sub.4].
Its structure was determined by MALDI-TOF MS and TOCSY, NOESY, HMQC
, and HMBC NMR spectroscopy.
Purity was checked by recording [sup.1]H-[sup.13]C NMR spectra and in standard correlation spectroscopy experiments (COSY, HMQC
)  in DMSO.