Spectral with DEPT data

In the study of poly(propylene oxide) (PRO, 55), Schilling and Tonelli applied NMR with DEPT spectral editing techniques to analyze microstmctures of commercial atactic and isotactic PPOs for their regiochemistry and end-group stmctures. DEPT data provided identification of methine,... 

Fig. 5.5.14 Schematic diagram showing how the double-phase encoded DEPT sequence achieves both spatial and spectral resolution within the reactor, (a) A spin-echo ]H 2D image taken through the column overlayed with a grid showing the spatial location within the column of the two orthogonal phase encoded planes (z and x) used in the modified DEPT sequence. The resulting data set is a zx image with a projection along y. In-plane spatial resol-ution is 156 [Am (z) x 141 [xm (x) for a 3-mm slice thickness. The center of each volume from which the data have been acquired is identified by the intersection of the white lines. The arrow indicates the direction of flow.

C-21 methyl protons. The C-3 and C-16 melhine protons appeared at 8 3.82 and 4.99, respectively. The downfield chemical shift values of C-3 and C-6 methine protons were indicative of the presence of geminal oxygen functionahties. The C-6 resonated at 8 5.36 while the sp hybridized C-28 methylene protons resonated as two singlets, integrating for one proton each, at 8 5.56 and 6.06. A combination of H and C-NMR spectral data indicated to us that compound 11 has a steroidal skeleton. A detailed interpretation of broad C-NMR and DEPT spectra revealed the presence of three metlyl, ten methylene, eight methine and five quaternary carbon atoms in 11. The stereochemistry at various chiral centers was estabhshed with the aid of NOESY spectrum. 

A schematic representation of how the double-phase encoded DEPT pulse sequence achieves spatial and spectral resolution within the fixed bed of ion-exchange resin is shown in Fig. 45. Typical data acquired in this experiment are shown in Fig. 46. The data were recorded from a vertical section through the center of the bed. The direction of superficial flow was from the bottom to the top of the bed. The spectra shown were recorded at regular intervals along the length of the bed, with a spatial separation of approximately 2.5 mm. With reference to Fig. 46, the... 

The multiplication of the FID s(t) with a factor a is equivalent to a multiplication of the spectrum S(f) with the same factor. This equivalence may be exploited e.g. in spectral editing to obtain multiplicity selective C subspectra from the DEPT-45, DEPT-90 and the DEPT-135 data. The multiplication with the corresponding factors may be performed with the DEPT FIDs or the DEPT spectra. 

A recent communication by Kumar and co-workers reported the isolation of a new binary tetrahydrocarbazole-indole alkaloid, methyl 2-methyl-4-(iV-2")8-methyl-l",2",3",4"-tetrahydrocarbazol-l"a-ylindol-3 -yl butanoate (77), C27H30N2O2 from the root timber of Murraya gleniei (67). It exhibited spectral data characteristic of an indole with an ester function. The mass spectral fragments having m/z 231 and 184 indicated that it was a binary alkaloid consisting of C14H17N02 and Q3H14N units. The structure and stereochemistry of 77 were established by the application of 1H, 13C, DEPT,... 

The structural assignment of the above cytochalasins was based primarily on their characteristic spectral data and direct comparison with previously known compounds. The mass spectrum of all metabolites showed a tropylium ion as the base peak (91 m/z) which is characteristic of 10-phenylcytochalasins and the molecular formulae of the six new compounds were established via high resolution MS and elemental analyses. Extensive H and 3C NMR analysis using COSY, HETCOR and DEPT NMR experiments, was also carried out in order to establish the reported structures. 

Determine the structure of a compound with the formula C10H12O2. In addition to the infrared spectrum and proton NMR, the problem includes tabulated data for the normal carbon NMR, DEPT-135, and DEPT-90 spectral data. 

Compound 1 was obtained as white powder. The molecular formula was determined as C41H66O12 by C NMR DEPT spectrum and FAB MS spectral data(m/z 773 [M+Na]. The IR spectrum indicated the presence of hydroxyl ( VmK 3400, 1070cm ) and carboxylic ester(v,Mx 1733cm ) groups. Acid hydrolysis of 1 yielded L-rhamnose and D-glucose identified by PC comparison with authentic samples. 

All (proton) NMR spectra were determined at 300 MHz, while the NMR spectra were obtained at 75 MHz. The H and spectra were determined in CDCI3 unless otherwise indicated. In some cases, the spectral data have been tabulated, along with the DEPT-135 and DEPT-90 data. Some of the proton NMR spectra have been expanded to show the details. Finally, all infrared spectra on liquid samples were obtained neat (with no solvent) on KBr salt plates. The infrared spectra of solids have either been melted (cast) onto the salt plate or else determined as a mull (suspension) in Nujol (mineral oil). 

You should inspect the values assigned to citronellol in the answers to Problem 3, along with the spectral data in Problem 4 for geraniol. The stacked full-edited DEPT on page 555 shows three methyl groups, three methylene groups, and two methine groups. C3 and C7 do not show in this spectrum. 

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