Carbon‐13 chemical shifts of some model carboxylic acids and esters

Couperus, P. A.; Clague, A. D. H.; Dongen, J.P.C.M. van

doi:10.1002/mrc.1270111203

Cited by 111 publications

(15 citation statements)

References 3 publications

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“…For the s-cis rotamers of a few members of this series such chemical shifts were reported by Couperus et al 18 The present results are in fair agreement with those values once the di †erent refer- …”

Section: Resultssupporting

confidence: 94%

Conformational effects on13C NMR parameters in alkyl formates

Kowalewski

Contreras

et al. 1998

Magn. Reson. Chem.

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Section: Resultssupporting

confidence: 94%

Conformational effects on13C NMR parameters in alkyl formates

Kowalewski

Contreras

et al. 1998

Magn. Reson. Chem.

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“…Six azelaoyl peaks with distinct chemical shifts and Figure 2 for labeling) since carbons 2 and 8 should be at the typical 13 C chemical shift region of covalently bound carbons to carbonyls from 34 to 48 ppm. 79 The peak labeled with f below 33.7 ppm is assigned to carbon 8 of the azelaoyl chain since we expect the remaining carbon 2 to have a similar chemical shift (close to 33.9) to the carbons 2 and 2′ of the POPC sn-1 and sn-2 chains, respectively. The high spectral resolution achieved allowed us to accurately determine the order parameters for all azelaoyl peaks except for the ones labeled a and f with order parameters too small for an accurate determination.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Acyl Chain Disorder and Azelaoyl Orientation in Lipid Membranes Containing Oxidized Lipids

Ferreira

Sood²,

Bärenwald

et al. 2016

Langmuir

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Oxidized phospholipids occur naturally in conditions of oxidative stress and have been suggested to play an important role in a number of pathological conditions due to their effects on a lipid membrane acyl chain orientation, ordering, and permeability. Here we investigate the effect of the oxidized phospholipid 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC) on a model membrane of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using a combination of (13)C-(1)H dipolar-recoupling nuclear magnetic resonance (NMR) experiments and united-atom molecular dynamics (MD) simulations. The obtained experimental order parameter SCH profiles show that the presence of 30 mol % PazePC in the bilayer significantly increases the gauche content of the POPC acyl chains, therefore decreasing the thickness of the bilayer, although with no stable bilayer pore formation. The MD simulations reproduce the disordering effect and indicate that the orientation of the azelaoyl chain is highly dependent on its protonation state with acyl chain reversal for fully deprotonated states and a parallel orientation along the interfacial plane for fully protonated states, deprotonated and protonated azelaoyl chains having negative and positive SCH profiles, respectively. Only fully or nearly fully protonated azelaoyl chain are observed in the (13)C-(1)H dipolar-recoupling NMR experiments. The experiments show positive SCH values for the azelaoyl segments confirming for the first time that oxidized chains with polar termini adopt a parallel orientation to the bilayer plane as predicted in MD simulations.

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“…Comparison of the I3C nrnr spectra of the three compounds 1, 2, and 12 indicated that the free carboxyl group of B (6c 183.5) is associated with the downfield carboxymethyl group 176.4) of the dimethyl ester 2. It is therefore assigned as the C-21 carboxyl group on the basis of normal I3C substitution rules (5). Thus compound B is 3,4-secotirucalla-4(28),7,24-trien-3,21-dioic acid 3-methyl ester 12.…”

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confidence: 99%

Tetranortriterpenoids and related compounds. Part 25. Two 3,4-secotirucallane derivatives and 2′-hydroxyrohitukin from the bark of Guareacedrata (Meliaceae)

Akinniyi¹,

Connolly²,

Rycroft³

et al. 1980

Can. J. Chem.

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24-trien-3,21-doc acid 1, the corresponding 3-monomethyl ester 12, and 2'-hydroxyrohitukin 13, have been isolated from the bark of Glrcrrecl cedrcttrr (Meliaceae). The structuresof 1 and 12 were confirmed by correlation with methyl 3-oxotirucalla-8.24-dien-21-oate (methyl isoelemonate) 6. The 'Hand I'C nmr data are reported.On a isole, de I'ecorce de Glrrrrrcl ceclrrrtcl (Meliaceae), trois triterpenoides nouveaux, I'acide 3,4-secotirucalla-4(28).7,24-tritn-3,21-dioique 1, son ester rnethylique 12 et 2'-hydroxyrohitukin 13. On a confirrne les structures 1 et 12 par une correlation avec methyl 3-oxotirucalla-8.24-dien-21-oate 6. Les spectres rmn sont presentks.In a continuation of our investigation (1,2) of the conditions the dimethyl ester 2 gave the chloroconstituents of the Meliaceae family we have diene 5 70.8 (s, C-25), 147.3, 137.6 (both s, C-8 examined the extract of the bark of G~iarea cedrata and C-9), 129.8 (s, C-4), 1 13.8 (t, C-28)). This and have isolated three new compounds, the ring A acid-induced isomerisation of a hindered trisubstisecotirucallane derivatives A 1 and B 12 and 2'-tuted to a tetrasubstituted double bond is reminishydroxyrohitukin 13, whose structures were as-cent of the behaviour of A7 tetracyclic triterpensigned on the following evidence.oids, e.g. odoratol (3), and, taken in conjunction Compound A 1, C3,H4,04, has spectroscopic with the above spectroscopic evidence, led us to 1 properties consistent with the presence of two car-as a biogenetically acceptable structure for comboxyl groups (ir: 3200-2500 (br), 1709 cm-1; 6c pound A. This was confirmed in the following way. 183.5 and 181.3), an exomethylene ( 6~ 4.80 (2H, Methyl 3-oxotirucalla-8,24-dien-21-oate 6, isobs); 6 c 132.4 (s) and 114.1 (t)), and two trisub-lated from elemi resin according to the procedure of stituted double bonds (tjH5.23 (m, H-7) and 5.09 (bt, Halsall and co-workers (4). was hydrogenated over H-24); 6,. 123.5 (d, C-24), 147.5 (s, C-25), and 1 18.0 palladium/charcoal to give the non-crystalline (d, C-7), 145.8 (s, C-8)). The molecule is therefore 24,25-dihydro-derivative 7. Baeyer-Villiger oxidatricarbocyclic. In addition there are three tertiary tion of 7 with peracetic acid afforded a mixture of methyls (6H 0.81, 0.87, and 0.95) and three vinyl the lactone 8 and the epoxylactone 9, separable by methyls ( 6~ 1.55, 1.65, and 1.75). Hydrogenation preparative tlc. The former was converted into the over palladium/charcoal of the dimethyl ester 2, diene dimethyl ester 11, via the hydroxy dimethyl obtained by reaction of 1 with diazomethane, af-ester 10, by alkaline hydrolysis, methylation, and forded the tetrahydroderivative 3 whose I3C nmr dehydration with thionyl chloride. Hydrogenation spectrum (6c 118.3 (d, C-7) and 145.6 (s, C-8)) of 11 yielded dimethyl 3,4-secotirucall-8-enclearly showed that one of the trisubstituted double 3,21-dioate 4, identical in all respects with the bonds was resistant to hydrogenation under normal product of acid isomerisation of dimethyl tetraconditions. On treatment with dry hy...

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Carbon‐13 chemical shifts of some model carboxylic acids and esters

Cited by 111 publications

References 3 publications

Conformational effects on13C NMR parameters in alkyl formates

Conformational effects on13C NMR parameters in alkyl formates

Acyl Chain Disorder and Azelaoyl Orientation in Lipid Membranes Containing Oxidized Lipids

Tetranortriterpenoids and related compounds. Part 25. Two 3,4-secotirucallane derivatives and 2′-hydroxyrohitukin from the bark of Guareacedrata (Meliaceae)

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