DEPT distortionless enhancement polarization

The carbon and DEPT (distortionless enhanced polarization transfer) spectra are shown in Figure 10. The HETCOR (heteronuclear two-dimensional proton-carbon correlation) spectrum is shown in Figure 11. The carbon assignments are listed in Table 5. Long-range HETCOR experiments were used to make the assignments for the thiophene carbons. 

DEPT (Distortionless Enhanced Polarization Transfer) is a more recent technique that provides the same information as off-resonance decoupling. DEPT is easier to run on modem, computer-controlled Fourier transform spectrometers. DEPT gives better sensitivity, and it avoids overlapping multiplets because all the peaks remain decoupled singlets. 

HSQC) or heteronuclear multiple quantum correlation (HMQC). The combined experiments such as 2D HSQC(HMQC)-TOCSY experiments are powerful tools for the assignment of the 13C and 11 resonances belonging to the same sugar residue providing enhanced dispersion of TOCSY correlations in the carbon dimension. More recendy, different carbon multiplicity editing methods, for example, DEPT (distortionless enhanced polarization transfer)-HMQC and E-HSQC, have been developed to reduce the complexity of proton-carbon correlation spectra and to enhance the resolution by narrowing the applied spectral window.11... 

The DEPT (distortionless enhanced polarization transfer) pulse sequence is probably one of the most widely used of all NMR experiments. It produces subspectra edited according to the number of protons bonded to each The DEPT pulse... 

The zero sum of intensities in a multiplet in these differential polarization transfer experiments means that any decoupling that causes all the lines to coalesce results in exact cancellation of intensities. Several methods have been devised to avoid this problem when decoupling is required. One is pulse-interrupted precession,which results in a net polarization transfer, as does the insertion of a properly chosen delay period in the INEPT sequence (as in Figure 12) so that all members of a multiplet appear positively enhanced, i.e., INEPT with refocusing (INEPTR). The DEPT (Distortionless Enhancement Polarization Transfer) sequence gives undistorted relative intensities of the multiplet components. 

The most widely used method for determining multiplicities of carbon atoms is DEPT (Distortionless Enhancement by Polarization Transfer). This has generally replaced the classical method of recording off-resonance C spectra with reduced CH couplings from which the multiplicity could be read directly. 

DEPT (distortionless enhancement by polarization transfer) A onedimensional C-NMR experiment commonly used for spectral editing that allows us to distinguish between CH, CH2, CH, and quaternary carbons. Detectable magnetization The magnetization processing in the x y -plane induces a signal in the receiver coil that is detected. Only single-quantum coherence is directly detectable. 

Multidimensional spectraas well as techniques including DEPT (distortionless enhancement by polarization transfer), COSY (correlated spectroscopy), and ROESY (rotating-frame overhauser enhancement spectroscopy) have been increasingly used. 

DEPT Distortionless enhancement by polarization transfer. A useful one-dimensional technique which differentiates methyl and methine carbons from methylene and quaternary carbons. 

Of the multitude of ID 13C NMR experiments that can be performed, the two most common experiments are a simple broadband proton-decoupled 13C reference spectrum, and a distortionless enhancement polarization transfer (DEPT) sequence of experiments [29]. The latter, through addition and subtraction of data subsets, allows the presentation of the data as a series of edited experiments containing only methine, methylene and methyl resonances as separate subspectra. Quaternary carbons are excluded in the DEPT experiment and can only be observed in the 13C reference spectrum or by using another editing sequence such as APT [30]. The individual DEPT subspectra for CH, CH2 and CH3 resonances of santonin (4) are presented in Fig. 10.9. 

Deoxyepinephrine, chemiluminescence, 647 Deoxygenation, hydroperoxides, 153 DEPT (distortionless enhancement by polarization transfer), 725 -6 6,9-Desdimethylartemisinin, synthesis, 288 Desferrioxamine, PfATP6 enzyme inhibition, 1313... 

Olive oil samples coming from 13 PDO Italian areas of production were analyzed by 13C NMR DEPT (distortionless enhancement by polarization transfer), a particular pulse sequence used to improve the signal-to-noise ratio of13 C spectra (Vlahov et al., 2001). Olive oils were dissolved... 

DEPT (Distortionless Enhancement by Polarization Transfer) Spectra... 

Now we are prepared to combine the APT (Section 12.10) and INEPT (Section 12.11.2) experiments into one of the most useful experiments in modem NMR. Like an APT spectrum, a DEPT (distortionless enhancement by population transfer) 13C spectrum is designed to display separate subspectra for CH, CH2, and CH3 carbon signals. And like an INEPT spectrum, signal intensity (i.e., sensitivity) arises by polarization transfer. 

DEPT, distortionless enhancement by polarization transfer DMF, dimethylformamide... 

An alternative pulse sequence that provides the same multiplicities as INEPT but with intensity ratios that follow the binomial theorem is DEPT (distortionless enhancement by polarization transfer).The pulse sequence, depicted in Fig. 12.3a, can be used, like refocused INEPT, for sensitivity enhancement but is usually employed as an editing technique. The three evolution periods T are chosen to approximate 1/2/, but the length of the pulse labeled 0 can be varied. As we show in the following, CH has maximum intensity at 0 = 90° CH2 has zero... 

The structural connectivity derived from examination of the 111, 13C/DEPT, DQF-COSY, HMQC, and HMBC data (DEPT = distortionless enhancement by polarization transfer DQF = double quantum filtering COSY = correlation spectroscopy HMQC = heteronuclear multiple quantum correlation HMBC = heteronuclear multiple bond correlation) resulted in global reevaluation of sclerophytin B structure and demonstrated that this compound and the related alcohol are not composed of two ether bridges as in the originally formulated structure 37, but share the structural features depicted as 38 <20000L1879>. Comparison of 13C and 111 NMR data of Norte s... 

NMR spectra. Chloroform was used as an internal standard for and C NMR spectra. All chemical shifts reported were externally referenced to tetramethylsilane (TMS). A DEPT (distortionless enhancement by polarization transfer) pulse sequence was used to obtain Si NMR spectra (6). 

One-dimensional subspectra also may be obtained by combining selective excitation and broadband homonuclear Hartmann mixing with het-eronuclear polarization-transfer steps like INEPT, DEPT (distortionless enhancement by polarization transfer), or heteronuclear Hartmann-Hahn transfer (Doss, 1992 Gardner and Coleman, 1994 Willker et al., 1994). Related experiments with multiple-step selective Hartmann-Hahn mixing in combination with heteronuclear coherence transfer were used by Kupce and Freeman (1993a). 

---