- Structure-odor correlations in homologous series of alkanethiols and attempts to predict odor thresholds by 3d-qsar studies
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Homologous series of alkane-1-thiols, alkane-2-thiols, alkane-3-thiols, 2-methylalkane-1-thiols, 2-methylalkane-3-thiols, 2-methylalkane-2-thiols, and alkane-1,??-dithiols were synthesized to study the influence of structural changes on odor qualities and odor thresholds. In particular, the odor thresholds were strongly influenced by steric effects: In all homologous series a minimum was observed for thiols with five to seven carbon atoms, whereas increasing the chain length led to an exponential increase in the odor threshold. Tertiary alkanethiols revealed clearly lower odor thresholds than found for primary or secondary thiols, whereas neither a second mercapto group in the molecule nor an additional methyl substitution lowered the threshold. To investigate the impact of the SH group, odor thresholds and odor qualities of thiols were compared to those of the corresponding alcohols and (methylthio)alkanes. Replacement of the SH group by an OH group as well as S-methylation of the thiols significantly increased the odor thresholds. By using comparative molecular field analysis, a 3D quantitative structure-activity relationship model was created, which was able to simulate the odor thresholds of alkanethiols in good agreement with the experimental results. NMR and mass spectrometric data for 46 sulfur-containing compounds are additionally supplied.
- Polster, Johannes,Schieberle, Peter
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p. 1419 - 1432
(2015/03/05)
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- Dipole-Stabilized Carbanions from Thioesters. Secondary α'-Lithio Carbamates and Tertiary α'-Lithio Thioesters
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The formation of 5 and 17, synthetic equivalents of the α-lithioalkylthio and α-lithiodialkylthio functions, respectively, by deprotonations of the corresponding carbamate 4 and thioester 16 are reported.The reactions of these formally dipole-stabilized carbanions with a variety of electrophiles and their use in synthese of 2,3-substituted thiiranes are demonstrated.The rearrangement of 17 to an α-thiol ketone is shown to be intramolecular by a double labeling experiment.Potentially chiral or conformationally isomeric α'-lithio thioesters are found to be racemized and equilibrated.Formations of secondary α'-lithio thioesters in medium chain, β'-dimethylamino, and allyl systems are reported while β'-alkoxy groups are shown to eliminate to give vinyl thio esters which undergo further metalation.The kinetic acidity of a methyl thioester is shown to be comparable to a propenyl thioester and greater then an ethyl thioester.
- Beak, Peter,Becker, Peter D.
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p. 3855 - 3861
(2007/10/02)
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