GRADIENT SUBMICRO INVERSE DETECTION - RAPID ACQUISITION OF INVERSE-DETECTED HETERONUCLEAR CHEMICAL-SHIFT CORRELATION DATA ON SUBMICROMOLE QUANTITIES OF MATERIAL

Micro NMR probes require substantially reduced quantities of sample fo r spectral characterization relative to traditional 5 mm probes. In ad dition, 3 mm micro probes have also made it feasible to routinely acqu ire inverse-detected heteronuclear shift correlation data on submicrom ole quantities. This paper reports the development and initial testing of a 1.7 mm submicro gradient inverse-detection probe. The further re ductions in the sample volume required relative even to the combinatio n of 3 mm micro probes and Shigemi micro NMR sample cells make it feas ible to acquire heteronuclear shift correlation data on submicromole q uantities of material in very short periods of time. Results obtained using a 0.55 mu mol sample of the model alkaloid cryptolepine dissolve d in 25 mu l of solvent are described. Using submicro probe technology , GHSQC data were acquired on the 0.55 mu mol sample of cryptolepine d issolved in 25 mu l as rapidly as 12 min and GHMBC data were recorded in 1.1 h. (C) 1998 John Wiley & Sons, Ltd.