DEPTQ: Distorsionless Enhancement by Polarization Transfer including the detection of Quaternary nuclei R. Burger and P. Bigler Multiplicity dependent 1D 13C-experiments such as DEPT, INEPT or APT belong nowadays to the most common and popular tools for the elucidation and characterization of moclecular structures on a routine level. In contrast to the less sensitive APT sequence DEPT and INEPT yield exclusively the signals of proton bearing carbons CHn, whereas the signals of quaternery carbons Cq are suppressed. As a consequence and to complete 13C data the latter two pulse sequences are usually combined with a simple one pulse 13C experiment. To avoid this additional experiment and to save spectrometer time the PENDANT pulse sequence has recently been proposed. In contrast to DEPT or INEPT the signals of all carbon types - including Cq - may be obtained together with the corresponding multiplicity information in one single experiment. Since it is based on the INEPT experiment the PENDANT pulse sequence is highly sensitive to deviations of pulse angles and delays from optimal values and may cause sporadic but severe problems as with olefinic methylene groups. Furthermore severe line distorsions are obtained for 1H-coupled PENDANT spectra. Most important however, this pronounced dependence on experimental parameters makes PENDANT especially less suitable for the generation of multiplicity selective subspectra (spectral editing), a procedure most successfully used in automatic spectral analysis. The aim of our efforts was to develop a pulse sequence based on DEPT yielding the signals of all carbon multiplicities including the signals of quaternary carbons and encompassing all of its advantages such as insensitiveness to experimental parameters and suitabilty for spectral editing. The correspondingly modified pulse sequence (DEPTQ) should be compared critically with PENDANT and the basic DEPT sequence. 可参考下面文章 http://www3.interscience.wiley.com/cgi-bin/fulltext/114210968/PDFSTART?CRETRY=1&SRETRY=0 展示一个图谱
Multiplicity editing including quaternary carbons: improved performance for the 13C-DEPTQ pulse sequence.
Magn Reson Chem. 2007 Jun;45(6):469-72
An improved version of the DEPTQ experiment yielding the signal and multiplicity information for all carbon types including the signals of quaternary carbons is proposed. It encompasses all the known advantages of the basic DEPT experiment. In comparison to the original version, signals of the sensitivity-limiting quaternary carbons are markedly increased: the initial 13C pulse may be adjusted to the Ernst angle, the NOE build-up period is prolonged by the split relaxation delay and a partial recovery of signal losses due to instrumental imperfections is achieved by the incorporation of composite adiabatic 13C refocussing pulses. Furthermore, pure absorption lineshapes for all carbon types are obtained with only one single scan. These attributes make this experiment attractive for 13C analysis of small molecules (including spectral editing), particularly in high-throughput analysis laboratories.
Multiplicity editing including quaternary carbons: improved performance for the 13C-DEPTQ pulse sequence An improved version of the DEPTQ experiment yielding the signal and multiplicity information for all carbon types including the signals of quaternary carbons is proposed. It encompasses all the known advantages of the basic DEPT experiment. In comparison to the original version, signals of the sensitivity-limiting quaternary carbons are markedly increased: the initial 13C pulse may be adjusted to the Ernst angle, the NOE build-up period is prolonged by the split relaxation delay and a partial recovery of signal losses due to instrumental imperfections is achieved by the incorporation of composite adiabatic 13C refocussing pulses. Furthermore, pure absorption lineshapes for all carbon types are obtained with only one single scan. These attributes make this experiment attractive for 13C analysis of small molecules (including spectral editing), particularly in high-throughput analysis laboratories. http://www3.interscience.wiley.com/cgi-bin/fulltext/114210968/PDFSTART
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