3 mm Probe technology

In 1993 shortly after 3 mm micro-probes became commercially available, an application of the use of 3 mm probe technology was reported by Hensens and coworkers at Merck.58 The enediyne antibiotic neocarzinostatin (9) is activated for duplex DNA cleavage by > 1000-fold by thiol reagents. Hensens and co-workers utilized both micro-inverse and micro-dual 3 mm NMR probes to characterize the structure and stereochemistry of the novel post-activated drug (10). 

Later in 1995, 3 mm probe technology was again utilized in the characterization of an indolobenzazepine, homocryptolepinone (17),66 which may be a biosynthetic constituent of the spiro nonacyclic alkaloid cryptospirolepine (18) also produced by C. sanguinolenta.61... 

Applications of 3 mm probe technology in the characterization of natural product structures continued unabated in 1999, with a number of papers appearing in the Journal of Natural Products that employed this technology. The first of these reports also came from the author s laboratory and described the characterization of a new oxobenzylisoquinoline alkaloid, thalprezwalskiinone (49) from Thalictrum prezwalskii.112... 

Work from the author s laboratory in 2000 first focused on the utilization HSQC-TOCSY data acquired using the sensitivity advantage of 3 mm probe technology as a facet of the assignment strategy for the severely congested spectra of polynuclear... 

An interesting biochemical application of 3 mm probe technology was reported by Williams and Hall129 in their studies of G[UUCG]C RNA tetraloops. Holscher... 

In another study, Blair and co-workers161 reported a novel lipid hydroperoxide-derived modification to arginine, again taking advantage of the sample size and sensitivity of 3 mm probe technology. 

In 1995, the author and co-workers reported a comparison of the 13C-NMR spectra acquired for an 100 pg sample of the alkaloid cryptolepicarboline (13) using both a 3 mm micro-dual and heteronuclear Nano-probes.61 The two probe technologies gave roughly the same s/n ratios with the Nano-probe allowing the acquisition of the spectra in roughly one-third of the time required in a conventional 3 mm probe. Sample volumes were 40 and 140 pL, respectively. 

Several applications of 3 mm micro-NMR probe technology were reported in 1994. The first utilized both a 3 mm micro-inverse probe as well as a heteronuclear Nano-probe to acquire the NMR data necessary for the characterization of a 30 pg (0.07 pmol) metabolite sample.59 Following the acquisition of a 13C reference spectrum using a heteronuclear Nano-probe the 40 pL sample from the nano-cell was quantitatively transferred to a 3 mm NMR tube and diluted to a total sample... 

There were a several additional studies of members of the indoloquinoline family of alkaloids isolated from Cryptolepis sanguinolenta reported that utilized 3 mm micro-NMR probe capabilities reported in 1995. The elucidation of the structure of quindolinone (16) was reported next and also utilized 3 mm micro-probe technology for the acquisition of a HMQC spectrum on an 800 pg sample of the... 

Musser and colleagues utilized 3 mm micro-probe technology in a study reporting the identification of a new series of fumonisins containing 3-hydroxypyridine moieties (24A-C).77 A 400 MHz 3 mm micro-dual probe was used to both record 13C spectra as well as for the acquisition of HMQC and HMBC data used in the characterization of these fungal secondary metabolites. 

In 1998, Serianni and co-workers88 again resorted to 3 mm micro-NMR probe technology in a report dealing with the detection and quantitation of the cyclic and acyclic forms of 13C-labeled aldopentoses. In a very interesting biosynthetic application, Rowe and co-workers89 investigated the conversion of <5-(L-amino-adipoyl)-L-cysteinyl-D-valine (30) to isopenicillin-N (31), an important step in the biosynthesis of penicillins and cephalosporins. The authors utilized 3 mm micro-NMR probe capabilities in their work in the analysis of the biosynthetic products of mutants of the enzyme isopenicillin-/V synthase, the enzyme normally responsible for the conversion of 30 to 31. 

In a series of three papers published in 1998, Schmitz and co-workers explored the chemical constituents of Micronesian marine sponges using 3 mm NMR probe technology. In the first of these papers, several imidazole alkaloids and their Zn + 2 complexes were isolated and characterized from the sponge Leucetta cf. chagosensis96... 

Moving into 1999, another report from a group at Oxford focused on the biochemistry of the /1-lactam antibiotic family, specifically the inhibition of series proteases by monocyclic /1-lactams. Once again this study exploited the sensitivity of 3 mm micro-probe technology.101... 

Logusch and co-workers105 further explored the capabilities of 3 mm NMR probe technology in a study of the enzymatic synthesis of a rodent metabolite the preemergence herbicide alachlor. Lipopolysaccharides from Chlamydia trachomatis serotype L2 were the subject of a study using a 2.5 mm Bruker micro-NMR probe reported by Rundt et al.106 This work represents the first complete structural characterization of a lipopolysaccharide from a Chlamydial sp. 

Next, Schmitz and colleagues116 reported the isolation and characterization of malayenolides AD, series of novel diterpenes from the Indonesian sea pen Veretillum malayense. The structures were elucidated using proton-detected 2D-NMR methods in conjunction with the use of 3 mm NMR probe technology. The structure of malayenolide-A (53) is shown. 

Next, Schmitz and co-workers119 reported the characterization of a pair of novel prenylated paracyclophanes and metacyclophane-type hydroquinones from the tunicate Aplidium longithorax. Complete H and 13C resonance assignments were made for these complex natural products, again employing 3 mm micro-probe technology. The structure of longitorhol-A (56) is shown. 

To illustrate this point, a comparison of the results obtained with a conventional 3 mm gradient inverse triple resonance and 5 mm cryogenic gradient inverse probe technology for the acquisition of long-range data was performed. Using a 2 mg sample of the... 

---