38172-86-0Relevant articles and documents
A Colorimetric Method for Quantifying Cis and Trans Alkenes Using an Indicator Displacement Assay
Valenzuela, Stephanie A.,Crory, Hannah S. N.,Yao, Chao-Yi,Howard, James R.,Saucedo, Gabriel,de Silva, A. Prasanna,Anslyn, Eric V.
supporting information, p. 13819 - 13823 (2021/05/17)
A colorimetric indicator displacement assay (IDA) amenable to high-throughput experimentation was developed to determine the percentage of cis and trans alkenes. Using 96-well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis or trans alkenes, depending upon their syn- or anti-addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis and trans alkenes. Blind mixtures of cis and trans alkenes were made, resulting in an average error of ±2 % in the percentage of cis or trans alkenes, and implementing E2 and Wittig reactions gave errors of ±3 %. Furthermore, we developed variants of the IDA for which the color may be tuned to optimize the response for the human eye.
Cork suberin molecular structure: Stereochemistry of the C18 epoxy and vic-diol ω-hydroxyacids and α,ω-diacids analyzed by nmr
Santos, Sara,Cabral, Vanessa,Graca, Jose
, p. 7038 - 7047 (2013/08/23)
Suberin is the biopolyester that protects the secondary tissues of plants against environmental variability and aggressions. Cork suberin is composed mostly of C18 ω-hydroxyacids and α,ω-diacids, 9,10-substituted with an unsaturation, an epoxide ring, or a vic-diol group. Although determinant for suberin macromolecular structure, the stereochemistry of these monomers is poorly studied, sometimes with contradictory results. An NMR technique was used here to assign the configuration of the 9,10-epoxy and 9,10-diol groups in C18 suberin acids, comparing the chemical shifts of diagnostic 1H and 13C signals with the ones of model compounds, before and after conversion of the vic-diol group into benzylidene acetal derivatives. The relative configuration was proved to be cis in the C18 9,10-epoxy and threo in the C18 9,10-diol suberin acids. These monomers were present in suberin probably as racemic mixtures, as shown by polarimetry. The revealed stereochemistry allows the suberin macromolecule to be built as an ordered array of midchain kinked C18 acids, reinforced by intramolecular hydrogen bonding.
Synthesis of enantioenriched methyl vic-dihydroxystearates
Plate, Mark,Overs, Michael,Sch?fer, Hans J.
, p. 1255 - 1258 (2007/10/03)
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.
