L3C-NMR spectral

The l3C NMR spectral properties of the parent heterocycles are summarized in Table 9. The signal for the pyrrole a-carbon is broadened as a result of coupling with the adjacent nitrogen-14 atom (cf Section 2.3.3.5). While the frequencies observed for the (3-carbon atoms show a fairly systematic upheld shift with increasing electronegativity of the heteroatom, the shifts for the a-carbon atoms vary irregularly. All the shifts are in the region of that for benzene, 8 128.7. 

Table 11 l3C NMR Spectral Data (ppm) for Dibenzo Heterocycles (in DMSO-rf6)a... 

H and l3C NMR spectral data for various anthocyanins are given in Tables FI.4.4 and FI.4.5. Typical1 H- H coupling constants for common anthocyanidins and their monosaccharides are given in Tables FI.4.6 and FI.4.7. 

Rh( 5-C9H7)( 74-COD)] (757)]. Calculation of the slip parameter from the l3C NMR spectral data of 73 gives a A<5(C3a,7a) = - 15 ppm 151), indicating that the hapticity of the ligand is best described as a distorted >/5-indenyl (759), in agreement with the crystallographic results. 

Proton and carbon-13 NMR spectroscopy can be regarded as outstanding tools for structural elucidations. The complicated equilibrium mixtures of 8-alkyl-substituted pterins and lumazines can be unraveled by a combination of H and l3C NMR spectral studies <86JOC246i, 92MI 718-07, 92MI 718-09). 

Table 5 l3C NMR Spectral Data of Parent Naphthyridines in CDCI3 (83Aho33i95, 147)... 

The l3C-NMR spectral data of benzo[a]quinolizidine compounds have been reported (154,282,283), and many examples from the isoquinoline alkaloids have been reviewed by Hughes and MacLean (284) (Volume XVIII, Chapter 3, in this treatise). As described in Section III, B, l3C-NMR spectroscopy, together with H-NMR and UV spectroscopy, has also played the leading role in the confirmation of the endocyclic double-bond structure in the dihydroisoquinoline moiety of 0-methylpsychotrine (7)... 

Table 12 l3C NMR Spectral Data for 1,3-Dichalcogenoles of Structure (41) in CDC13... 

Perhydrothiazolo[3,4-fl]pyridine adopts a 60% trans-fused (179) 40% cis-fused (180) equilibrium in CDCI3-CFCI3 at 193 K. The c7s-(l-H, 8a-H)-1-methyl derivative favors exclusively the trans-conformer (181), whereas the epimer adopts an 87% trans-fused (182) 13% cis-fused (183) conformational equilibrium at 193 K. The pair of 6-ethyl substituted derivatives adopts the trans- and cis-fused conformations (184) and (185). These assignments were based on H- and l3C-NMR spectral data [68T2485 88JCS(P1)1173]. 

Compound D is isomeric with compound C (Problem 13.57) and has the following l3C NMR spectral data. Propose a structure. 

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