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Detection 2D NMR

In S-N compounds containing H bonded directly to nitrogen, inverse detection 2D NMR spectroscopy can be applied to give N... [Pg.35]

Recourse to innovations in NMR spectroscopy is essential for further advances in the investigation of complex saponins. The use of a 600 MHz spectrometer gives the required sensitivity, consistent with the low amounts available by modern isolation techniques, while the use of sequential ID and inverse-detected 2D NMR techniques, couples the short time necessary to perform the experiments with the selfconsistency of the obtained results and, thus, the unambiguous structure assignment [128]. [Pg.210]

Later in 1996 the first example of a dimeric indoloquinoline alkaloid, crypt-omisrine (22), was isolated and its structure elucidated.73 Inverse-detected 2D-NMR spectra were recorded using a 3 mm micro-inverse probe 13C chemical shift data were recorded for the sample using a 3 mm micro-dual probe. In addition to the mass spectral data, a 0.9% nuclear overhauser effect (NOE) observed between the HI and H9 protons was used to confirm the structure. [Pg.37]

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. [Pg.51]

Martin, G. E. and Crouch, R. C. (1994) Inverse-Detected 2D NMR Applications in Alkaloid Chemistry,... [Pg.466]

There is, in fact, one disadvantage associated with acquiring a signal by means of gradients gradient versions of various 2D experiments exhibit a 2 / decrease in sensitivity with respect to their nongradient counterparts. This is, however, seldom a serious problem, especially with the proliferation of H-detected, 2D NMR experiments. [Pg.251]

An interesting study reported in 2001, although it did not utilize any inverse-detected 2D NMR data, did report a wealth of useful chemical shift data for parent azoles and benzazoles. Solid-state chemical shift data were reported for several pyrazole analogues by Alvarez-Larena. Trofimenko et al reported a study of the buttressing effects of the A-tert-h xiy group of a series of pyrazoles in the solid state, followed by a study by Claramunt and co-workers of a series of halo triazoles. Martins and co-workers reported data for a series of 5-trichloromethyl-1,2-dimethyl-1/f-pyrazolium chlorides. Malpass and co-workers reported direct observe chemical shift data for a series of bicyclic amines and lactams. Recently, a large body of chemical shift data for a series of l,4-diazaspiro[4.5]decanes and l,4-oxazaspiro[4.5]-decanes using direct observe methods were reported by Ariza-Castolo and co-workers. " Readers with an interest in the chemical shift behavior of these systems are directed to these references as a source of data. [Pg.33]

G. E. Martin and R. C. Crouch, Inverse-detected 2D NMR applications in alkaloid chemistry, in Modern Methods of Plant Analysis, vol. 15, H. F. Linskens and J. F. Jackson, eds. Springer-Verlag. Berlin, 1994, pp. 25-89. [Pg.97]

The inverse-detected 2D NMR experiments that have been discussed to this point have all been discrete, single-purpose experiments, e.g. correlating protons with their directly bound heteronucHde (typically or N). There are another class of inverse-detected 2D NMR experiments that are generally referred to as hyphenated 2D experiments. These are experiments that first establish one type of correlation, followed by an additional experiment segment that then pursues a further spectroscopic task. Predecessors of the inverse-detected variants of these experiments were the HC-RELAY (proton—carbon heteronuclear relayed coherence transfer) experiments pioneered by Bolton [151—155]. Examples of these include, but are by no means hmited to HXQC-COSY and -TOCSY [156—158], -NOESY [159], -ROESY [160], and more recent gradient variants [161] etc., where X = S (single) or M (multiple) quantum variants of the experiments. [Pg.252]

A number of Fi region-selected inverse-detected 2D NMR experiments have been reported. One of the earliest (Davis 1989) took a different approach from more recent reports. Recognizing the need for higher digital resolution in assigning peptide spectra, Davis approached Fi region selection... [Pg.52]

The earliest application of inverse-detected 2D NMR techniques to a terrestrial alkaloid of which we are aware was the assignment of the H and NMR spectra of the indolocarbazole alkaloid staurosporine (7) reported by Meksuriyeri and Cordell (1988). Later in 1988, Edwards et al. utilized HMQC in the elucidation of the structure of pumiliotoxin-A (10) and related indolizine alkaloids isolated from Panamanian poison frogs. These were the only applications of inverse-detected 2D NMR techniques in alkaloid to appear in 1988. We will thus begin with staurosporine (7) and proceed to related carbazole-based alkaloids before continuing to pumiliotoxin-A (10) and other terrestrial alkaloids. [Pg.56]

Neocarazostatins. The next reported application of inverse-detected 2D NMR to a terrestrial carbazole alkaloid did not appear until 1991 in the report of Kato et al. A series of free radical scavenging compounds, neocarazostatins A-C, were isolated from a Streptomyces sp. strain. The structure of neocarazostatin-A (9) is shown below. Long-range connectivities from an HMBC spectrum (not referenced) were used in assigning the attachments of the two side chains to the carbazole nucleus. [Pg.58]

Digressing, we noted above that the other 1988 application of inverse-detected 2D NMR was to indolizine alkaloids of the pumiliotoxin-A and allopumiliotoxin classes (Edwards et al. 1988). A total of ten alkaloids were... [Pg.58]

Another reported application of inverse-detected 2D NMR was the 1989 elucidation of the structure of the diterpene alkaloid lassiocarpine (11) (Takayama et al. 1989). This study utilized both HMQC to establish one-bond correlations and HMBC to obtain long-range connectivity information to link the structural components elucidated by other means together. [Pg.59]

Perhaps the largest single group of terrestrial alkaloids to which inverse-detected 2D NMR techniques have been applied are the diverse indole-derived/containing alkaloids. [Pg.59]

Isoreserpiline, Tetraphylline, and Reserpiline Hydrochloride. Inverse-detected 2D NMR was also utilized in 1989 to establish direct-proton carbon shift... [Pg.59]

Our study of cryptolepine, performed on 5 mg of material dissolved in 0.8 ml of DMSO-d6, highlights what will probably become an increasingly common protocol as inverse-detected 2D NMR methods become more widely implemented. Typically, we acquire a proton reference spectrum followed by COSY and HMQC spectra. On the sample in question here. [Pg.60]

Macwxine. The sole application of inverse-detected 2D NMR techniques to an oxindole was in the elucidation of the structure of macroxine (15)... [Pg.64]

Dehydroaspidospermine. An interesting application of inverse-detected 2D NMR techniques was reported in conjunction with a study of the flow thermolysis of 1,2-dehydroaspidospermidine (16) by Hugel et al. (1991). [Pg.64]


See other pages where Detection 2D NMR is mentioned: [Pg.289]    [Pg.25]    [Pg.40]    [Pg.87]    [Pg.74]    [Pg.25]    [Pg.27]    [Pg.29]    [Pg.33]    [Pg.35]    [Pg.37]    [Pg.39]    [Pg.41]    [Pg.45]    [Pg.47]    [Pg.49]    [Pg.51]    [Pg.53]    [Pg.55]    [Pg.56]    [Pg.56]    [Pg.57]    [Pg.57]    [Pg.59]    [Pg.60]    [Pg.61]    [Pg.63]    [Pg.63]    [Pg.65]    [Pg.65]    [Pg.67]   
See also in sourсe #XX -- [ Pg.149 ]

See also in sourсe #XX -- [ Pg.131 ]




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