Monolayer studies of methyl vic-dihydroxyoctadecanoates

Jacobi, S.; Chi, Lifeng; Plate, Mark; Overs, Michael; Schäfer, Hans J.; Fuchs, Harald

doi:10.1016/s0040-6090(98)00624-5

Cited by 23 publications

(16 citation statements)

References 16 publications

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“…Results on the chiral discrimination of monolayers of (-)-(9 S ,10 S )-4c and (+)-(9 R ,10 R )-4c as determined by Brewster angle microscopy on the Langmuir trough and the formation of gels consisting of helical fibers as observed by atomic force microscopy are reported elsewhere. 11 The solvents were purified and dried, if necessary. …”

Section: Synthesis Of Enantioenriched Methyl Vic -Dihydroxystearatesmentioning

confidence: 99%

Synthesis of Enantioenriched Methyl vic-Dihydroxystearates

1998

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Several enantioenriched methyl vic -dihydroxystearates 4 have been synthesized from methyl octadecenoates by enantioselective dihydroxylation in good yields (85-97%) and with satisfactory enantiomeric excess (ee 80-97%). The enantioenriched anti -9,10-dihydroxystearates ( anti -4c ) were prepared by HPLC separation of the corresponding dicamphanyl esters anti -6 . Their ee was determined by HPLC of the corresponding diastereoisomeric carbamates 7 , and their configuration was assigned by relation to a described compound or by applying the mnemonic device of Sharpless.Monolayers of chiral amphiphiles can spontaneously separate into chiral domains. 1 Most of the amphiphiles, studied so far bear chiral polar head groups. We wanted to explore how the monolayer behavior of methyl stearates is influenced by stereogenic centers located at different positions in the alkyl chain. For this purpose enantioenriched methyl vic -dihydroxystearates were prepared using the Sharpless 2 method for the enantioselective dihydroxylation of olefins. The corresponding methyl octadecenoates were synthesized by Kolbe electrolysis 3 or Wittig reaction. Methyl octadec-17-enoate (3a) has been obtained in 40% yield by coelectrolysis of one equivalent of undec-10-enoic acid (2) with four equivalents of methyl azelate (1) 4 (Scheme 1) at platinum electrodes in methanol in an undivided cell. 5 Ethyl trans -octadec-2-enoate (3b) was synthesized by a Wittig reaction from hexadecanal and (ethoxycarbonylmethylene)triphenylphosphorane in 74% yield.The synthesis of chiral vicinal diols by enantioselective dihydroxylation has been described for a variety of olefins; 2 however, to our knowledge this powerful conversion has not yet been applied to the synthesis of chiral vicdihydroxy fatty acid esters. The enantioselective dihydroxylation of 3a , b and of commercially available methyl trans -octadec-9-enoate (3c) led in excellent yield (85-97%) and satisfactory to high enantiomeric excess (ee 84-97%) to methyl vic -dihydroxystearates 4 (Scheme 2, Table 1). As reagents for the dihydroxylations commercially available AD-Mix-α and AD-Mix-β were used. 6In the case of methyl oleate (5) the enantiomeric excess of the dihydroxylation was very low, which has been reported before for the dihydroxylation of nearly symmetrical cisolefins. 7 The synthesis of enantioenriched methyl anti -9,10-dihydroxystearates was then achieved by HPLC separation of the corresponding diastereoisomeric dicamphanyl esters anti -6 (Scheme 3). For this purpose methyl oleate (5) was treated with OsO 4 to yield the methyl anti -9,10-dihydroxystearates ( anti -4c ). 8 The diastereoisomers anti -6 were obtained by diesterification of anti -4c with (-)-camphanic acid chloride, as described by Mohr and Rosini, 9 followed by HPLC separation and partial hydrolysis to the methyl anti -9,10-dihydroxystearates (-)-(9 S ,10 S )-4c and (+)-(9 R ,10 R )-4c (Scheme 3, Table 2).To determine their enantiomeric purity, the dihydroxy esters 4a , syn-4b and anti-4c were transformed into their diastereoiso...

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Section: Synthesis Of Enantioenriched Methyl Vic -Dihydroxystearatesmentioning

confidence: 99%

Synthesis of Enantioenriched Methyl vic-Dihydroxystearates

1998

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“…Lipid monolayers having a second polar group that are substituted at the lipophilic alkyl chain have been frequently studied as model systems because they are constituents of the structural architecture of biological membranes and, thus, abundant in biological systems. [1][2][3][4][5][6][7][8] The biomembrane characteristics are modied in a unique way by the positions of the secondary polar OH group in the alkyl chain of the lipid. 2 Therefore, hydroxy fatty acids have been good candidates for the characterization of the effect of a second polar group substituted at different positions of the alkyl chain.…”

Section: Introductionmentioning

confidence: 99%

Quantum chemical analysis of the thermodynamics of 2D cluster formation of 2-hydroxycarboxylic acids at the air/water interface

et al. 2013

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In the framework of the quantum chemical semiempirical PM3 method, the thermodynamic and structural parameters of formation and clusterization were calculated for 2-hydroxycarboxylic acids with the general formula C n H 2n+1 CHOHCOOH (n ¼ 5-15). Dimers and tetramers were formed on the basis of optimized monomer structures. It was shown that the alkyl chains in the considered associates orientate themselves with the following values of the tilt angles with respect to the pand q-directions of the interface: d ¼ 7.2-21.2 and 4 ¼ 9.8-21.1 depending on the monomer structure of the cluster.Comparing the Gibbs energy values of clusterization for small aggregates, a possible scheme of 2D clusterization is proposed based on the formation of linear aggregates constructed by dimers with 'parallel' orientation of the functional groups for 2-hydroxycarboxylic acid monomers with n # 16 carbon atoms in the alkyl chain. The following parameters of the unit cell for the most energetically preferred structure of 2D film 3 were found: a ¼ 4.85 Å, b ¼ 5.41 Å, and the angle between them q ¼ 95 . The molecular tilt angle of 2-hydroxycarboxylic acids with respect to the air/water interface was calculated to be t ¼ 21.7 . The spontaneous clusterization threshold is 14 carbon atoms in the 2-hydroxycarboxylic acid chain at the air/water interface for a monolayer built on the basis of monomer 3 in good agreement with the existing experimental data.

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“…Comparing the behaviors probed in the pure acid, hydroxy acid (this work) and dihydroxy , acid systems on a pure water subphase illustrates the role the hydroxy group plays in defining monolayer phase behavior. The hydrophilic nature of the hydroxy group and its capacity for hydrogen bonding dominates the system, with the formation of a complex multiphase film, the specificities of which are temperature and pressure dependent.…”

Section: Resultsmentioning

confidence: 75%

Nonequilibrium 2-Hydroxyoctadecanoic Acid Monolayers: Effect of Electrolytes

Lendrum

Ingham²,

Lin

et al. 2011

Langmuir

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2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position α to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of ∼6. The role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase.

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Monolayer studies of methyl vic-dihydroxyoctadecanoates

Cited by 23 publications

References 16 publications

Synthesis of Enantioenriched Methyl vic-Dihydroxystearates

Synthesis of Enantioenriched Methyl vic-Dihydroxystearates

Quantum chemical analysis of the thermodynamics of 2D cluster formation of 2-hydroxycarboxylic acids at the air/water interface

Nonequilibrium 2-Hydroxyoctadecanoic Acid Monolayers: Effect of Electrolytes

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