H NMR spectra

The spectrum of 2-hydroxy-7-0-methylscillascillin (20) is quite complex. Due to the hemiacetal structure the compound shows mutarotation 44). The mixture of the diastereomeric forms gives rise to a double set of signals for most protons. Data for the 2 a- and 2P-hydroxy compounds (20 a) and (20 b) are presented in Table 4. 

The signals of the benzylic protons (5 3.6), the gem-dimethyl group (1.66, 1.83) and the vinylic proton (8 5.35) as, for example, in heptaphyl-line (9) are diagnostic for the 3 3 dimethyl allyl side chain (abbreviated as DMA). The doublets for each of the olefinic protons (J = 10 Hz) at 56.25 and 5.4 respectively together with the signal for the gem-dimethyl group on the carbon linked to the oxygen are indicative for the 

2 2 -dimethyl-A pyran system (abbreviated as DMP) fused to a car-bazole skeleton as in girinimbine (3). In compounds of the mahanimbine (10) type one of the methyls of a DMP system is replaced by a chain of 6-carbons, producing the expected changes in the spectrum. The mutually chelated hydroxyl and formyl groups exhibit signals of the aldehydic proton at 89.30 and the hydroxyl beyond 5 10.00. In Table 3, HNMR data of the alkaloids reported after 1977 (18) are briefly summarised (the signals of the NH proton are not included). 

Downfield Shift Value of peri-Proton in Cyclized Products 284, 290, 291, and 406 

The deshielding influence of the carbonyl group at the 3-position on methylene protons at the 2-position in the condensed 4-thiazolidinones is also observed. The signal of the methylene protons appeared at low field compared to that of the dihydro series of condensed thiazoles (Table III). This offers proof that the acid has undergone cyclization resulting in the synthesis of condensed 4-thiazolidinones, although it does not help in deciding the orientation of cyclization. 

The room-temperature H NMR spectrum of 2-acetylperhydropyr-ido[l,2-c]pyrimidine exhibits signals arising from both rotational isomers (56c and 56t), as a result of restricted rotation about the N —COMe bond. The cis and trans isomers 56c and 56t could be distinquished on the basis of /gem for the protons of the methylene group adjacent to the amido N, and the chemical shift of l-H q [730MR(5)397]. 

The H NMR spectrum of 57d in CDCI3-CFCI3 solution at 19°C indicates an equilibrium mixture containing 45% of the pyrido[l,2-c]pyrimidinium ion (58), 27% of the dimer (57d), and 28% of the monomer (57m) [79JCS(P2)504], At -45°C, only the signals of the dimer (57d) could be assigned in the spectrum. 

The coupling constants between llb-H and the C(l) methylene protons (14 and 6 Hz, and 9 and 3 Hz) for 9,10-dimethoxy-4-phenyl-l,6,7,llft-tetrahydro- and 1,3,4,6,7,llft-hexahydro-2//-pyrimido[6,l-a]isoquinolines indicate the predominance of the N-inside cis conformation (84JHC149). 

The H NMR spectra of 3-methyl- and 3-phenyl-l,3,4,6,7,llft-hexahydro-2/f-pyrimido[6,l-fl]isoquinoline-2,4-diones in CDCI3 are very similar to each other, and the magnitudes of the coupling constants involving the 

C(6) and C(l) methylene protons are consistent with the Irans-fused conformation (91MRC1040). 

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Figure 6.1, H NMR spectra of (a) the tert-butyl cation [trimethylcarbenium ion, (CH jj-jC ] [b) the tert-amyl cation [dimethyletbylcarbenium ion, (CH3)3C -C2H 5] and (c) the isopropyl cation [dimethylcarbenium ion, (CH3)2C Hj (60 MHz, in SbF5 S02CIF solution, —60°C).

Figure 1. H NMR spectra of PPO (I), PPO modified with benzene-sulfonyl chloride (Sample No. 2, Table III) (II), and PPO modified with p-toluenesulfonyl chloride (Sample No. 4, Table III) (III) Reproduced with permission from Ref. 17. Copyright 1987, Wiley.)...

Ervatamine (44) had a different conformation in solution with respect to 45 and 50. This was deduced from the different rate of N-methylation and from a careful inspection of 1 H-NMR spectra. These studies led to proposed conformation 270 for 44 and conformations 271a,b for 45 and 50, respectively. 

Figure 1 H NMR spectra of representative nonaromatic pyrans and fused pyrans...

Figure 1.3 1 H NMR spectra (400 MHz) of chloroform recorded at flow rates of (a) 9...

Figure 1.15 The 1 H NMR spectra of 12 xg retinoic acid in ACN/D20 (60/40), (a) without and (b) with solvent signal suppression...

Figure 3.3 Expansions of the 750 MHz 1 H NMR spectra for key peaks in the chiral HPLC-NMR spectra for the different isomers of atracurium besylate...

Figure 3.10 Comparison of lipoprotein standards and HPLC-resolved lipoproteins, (a) Partial 600 MHz HPLC-1 H NMR spectra (80.5-2.0) of the HDL, LDL and VLDL fractions separated by using directly coupled HPLC-NMR spectroscopy at 15.5, 58.9 and 86.6 min, respectively, (b) Partial 600 MHz 1H NMR spectra (8 0.5-2.0) of standard (std) HDL, LDL and VLDL. Abbreviations VLDL1, LDL1 and HDL1 indicate the resonances from the terminal methyl groups of the mobile fatty acid chains bound in the various lipoproteins VLDL2, LDL2 and HDL2 indicate resonances from the methylene groups of the mobile fatty acid chains...

Figure 3.11 Separation of a mixture of three barbiturates using HPLC-NMR with superheated D2O as eluent, showing the 1 H NMR spectra of the three separated substances...

Figure 7.1.14 1 H NMR spectra of the separated chlorinated oligomers obtained from the...

Fig. 7.1 shows a typical H-NMR spectrum obtained with the partially purified, microbubble surfactant mixture prior to monolayer formation. For comparison, Table 7.1 gives the chemical-shift data for the proton resonances that can be readily identified in the 1 H-NMR spectra of long-chain acyl lipids (ref. 395-401). 

The collected microbubble-surfactant monolayer material was subsequently lyophilized and redissolved in CD3OD. As with the preceding NMR measurements (see Section 7.1), H-NMR spectra at 270 MHz were obtained with the same Bruker Hx-270 NMR spectrometer. In this case, approximately 0.5% solutions (w/v in CD3OD) of the microbubble-surfactant monolayer material were employed in the measurements (all taken at 26°C). Tetra-methylsilane was used as an internal reference standard (ref. 394). 

Full details of the previously discussed (1) H NMR spectra of evonine and neoevonine have now been published. (182) The positions of the acetate functions in evonimine [284] have been determined by comparison (Table V) of the spectrum with that of the pentadesacetyl... 

Fig. 3.33 1 H-NMR spectra showing the increase in the O/l ratio of DPPC vesicles in the presence of 50 mM decan-1 -ol. (a) After incubation, O/l ratio = 1.58. (b) After six cycles, O/l ratio = 1.92 (% lysis = 11.6). (c) After 10 cycles. O/l ratio = 2.25 % lysis = 20.6) (Reprinted from Fig. 3 of ref. 121 with permission from Elsevier Science.)...

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