COLOC spectra

Like the HMBC, the COLOC experiment provides long-range hetero-nuclear chemical shift correlations. The COLOC spectrum, H-NMR, and C-NMR data of 7-hydroxyfrullanolide are presented here. Use the data to assign the quaternary carbons. 

COLCX experiments. In the COLOC spectrum (/=4.2 Hz), a C-10 quaternary carbon (S 157.49) was correlated with the methoxy protons ((5 3.95) and the C-8 aromatic proton (S 7.75). The NOE experiment showed a cross-peak between the methoxy protons (5 3.95) and two aromatic protons (H-9 and H-11). Eurthermore, an NOE was observed between the aromatic (H-11) and methyl protons (H -6, S 2.33). These data establish the presence of this additional methoxy group ( 3.95) at C-10. Based on these spectral data, and the structural similarity to (+)-staurosporine, the structure 296 was assigned to TAN-999 (293) (Scheme 2.74). 

Figure 6 2S The COLOC spectrum of vanillin. (Reproduced from H. Duddeck and W. Dietrich, Structure Elucidation hy Modern NMR, Stcinkopff Verlag, Darmstadt, Germany. 1989, p. 24.)...

The H-NMR, 13C-NMR, and LL1 COSY spectra revealed the presence of the same partial structures as in 104, a phenyl group, a 3-methoxy-4,5-methylenedioxyphenyl group, a trisubstituted double bond, and two acetoamides. The spectra also indicated the presence of a -CH2-CH-CH2- moiety. These partial structures were connected from the COLOC spectrum, and the whole structure of 105 was determined to be 1,4-diacetyl-2-benzyl-5-(3-methoxy-4,5-methylenedioxybenzyl)-... 

COLOC) spectrum. The relative structure of casearin A (12) was established on the basis of the coupling constants of each proton and the nuclear OVerhauser effect (NOE) correlated spectrum. The structures of casearins B - R (13 - 29) were determined by comparing their spectral data with those of casearin A (12). Also, the absolute structures of casearins shown in Fig. 4 were confirmed by X-ray analysis of casearin B (13) and exciton chirality method of the allylic benzoate derivative of casearin C (14). 

Conditions CDCI3, 25 °C, 200 MHz ( //), 50 MHz ( C). (a) CH COSY (shaded contours) and CH COLOC diagrams (unshaded contours) in one diagram with enlarged section (b), and with expanded methoxy quartets (c) (d) sections of C NMR spectra, each with //broadband decoupled spectrum below and NOE enhanced coupled spectrum (gated decoupling) above. 

First the five protons (integral) of the //NMR spectrum (Sfj = 7.50 - 7.94) in the chemical shift range appropriate for aromatics indicate a monosubstituted benzene ring with typical coupling constants 8.0 Hz for ortho protons, 1.5 Hz for meta protons.). The chemical shift values especially for the protons which are positioned ortho to the substituent Sn = 7.94) reflect a -M effect. Using the CH COLOC plot it can be established from the correlation signal hclS = 66.AI7.94 that it is a benzoyl group A. 

Example 2. Vinviidene Chloride Isobutylene Copolymer. The next example is for the carbon-13 spectrum of copolymer vinylidene chloride isobutylene. Figure 5 shows the full spectrum and the peak assignment listing for the non-protonated vinylidene chloride carbon in the 84-92 ppm range. Triad assignments were made (Crowther, M. W., 1987, Syracuse University, unpublished data) using the two-dimensional COLOC (20) experiment. There are ten v-centered pentads representing different environments for the vinylidene chloride carbon. The i represents the non-protonated carbon in the isobutylene polymer unit. 

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