Applications of cryogenic NMR probe technology to long-range H-1-N-15 2D NMR studies at natural abundance

The development of new NMR probe technologies has been an active area of re search effort for the past decade. Recently, cryogenically cooled NMR probe s have been the subject of considerable interest in the light of the large gains in sensitivity and hence savings in spectrometer time that can be rea lized by utilizing this technology. With low gamma nuclides, such as N-15, time savings may be less of an issue than the ability to work with availabl e samples rather than having to isolate additional material for analysis. R esults of 5-10 Hz optimized CIGAR-HMBC H-1-N-15 experiments at natural abun dance obtained using a 5 mm Varian H-1-N-15 Cryo-Q NMR probe are compared w ith those from a 3 mm gradient inverse triple resonance probe using a 2 mg sample of the oxazolidinone antibiotic eperezolid in a 3 mm NMR tube. Using the cryogenic NMR probe, a H-1-N-15 CIGAR-HMBC spectrum in which most prev iously reported long-range couplings are observed was recorded in similar t o 10 min; almost all of the expected long-range responses were observed wit hin 26 min. Acquiring the same data set with identical parameters using a c onventional 3 mm gradient inverse triple resonance probe gave data that wer e of substantially lower quality. Acquiring data comparable to the 26 min c ryogenic probe data with the conventional 3 mm probe required similar to4 h to observe all of the responses and similar to 18 h to obtain a spectrum w ith a signal-to-noise ratio comparable to the data set acquired with the cr yogenic NMR probe. Copyright (C) 2001 John Wiley & Sons, Ltd.