1.Components of ether-insoluble resin glycoside (rhamnoconvolvulin) from rhizoma jalapae braziliensis.
Ono M1, Nishioka H, Fukushima T, Kunimatsu H, Mine A, Kubo H, Miyahara K. Chem Pharm Bull (Tokyo). 2009 Mar;57(3):262-8.
Alkaline hydrolysis of the ether-insoluble resin glycoside (convolvulin) fraction of the roots of Ipomoea operculata (GOMES) MART. (Convolvulaceae) afforded a glycosidic acid named operculinic acid H along with isovaleric, tiglic, and exogonic (3,6:6,9-diepoxydecanoic) acids. Operculinic acid H was characterized to be 3S,12S-dihydroxyhexadecanoic acid 12-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)-[O-beta-D-glucopyranosyl-(1-->3)]-O-beta-D-glucopyranosyl-(1-->2)-[O-alpha-L-rhamnopyranosyl-(1-->6)]-O-beta-D-glucopyranoside on the basis of spectroscopic data and chemical evidence. The absolute configuration of exogonic acid determined from the alpha-methoxy-alpha-trifluoromethylphenylacetic acid esters of the hydrogenolysis products revealed that exogonic acid exists as a mixture (ca. 1 : 1) of two epimers, (3S,6S,9R)- and (3S,6R,9R)-diepoxydecanoic acids.
2.New efficient chiral derivatizing agent, alpha-cyano-alpha-fluoro(2-naphthyl)acetic acid (2-CFNA). application to the EE determination of (-)-3-acetoxy-2-fluoro-2-(hexadecyloxymethyl)propan-1-ol.
Takahashi T1, Fukushima A, Tanaka Y, Segawa M, Hori H, Takeuchi Y, Burchardt A, Haufe G. Chirality. 2000 Jun;12(5-6):458-63.
The new chiral derivatizing agent (CDA), alpha-cyano-alpha-fluoro(2-naphthyl)-acetic acid (2-CFNA) 1 was prepared in optically pure form by chiral HPLC separation of racemic 2-CFNA methyl ester (2-CFNA Me ester) (+/-)-2. The ester was obtained by fluorination of methyl alpha-cyano(2-naphthyl)acetate with FClO3. 2-CFNA 1 has proven to be a significantly superior CDA for determination of enantiomeric excess (ee) of a primary alcohol when compared to alpha-methoxy-alpha-trifluoromethylphenylacetic acid (MTPA, Mosher's agent) and alpha-cyano-alpha-fluoro(p-tolyl)acetic acid (CFTA). The ee of (-)-3-acetoxy-2-fluoro-2-(hexadecyloxymethyl)propan-1-ol (-)-9, a fluorinated analog of anticancer active ether lipids, was determined using (+)-2-CFNA (+)-1.
3.Mosher ester analysis for the determination of absolute configuration of stereogenic (chiral) carbinol carbons.
Hoye TR1, Jeffrey CS, Shao F. Nat Protoc. 2007;2(10):2451-8.
This protocol details the most commonly used nuclear magnetic resonance (NMR)-based method for deducing the configuration of otherwise unknown stereogenic, secondary carbinol (alcohol) centers (R1R2CHOH (or the analogous amines where OH is replaced by NH2)). This 'Mosher ester analysis' relies on the fact that the protons in diastereomeric alpha-methoxy-alpha-trifluoromethylphenylacetic acid (MTPA) esters (i.e., those derived from conjugation of the carbinol under interrogation with MTPA) display different arrays of chemical shifts (deltas) in their 1H NMR spectra. The protocol consists of the following: (i) preparation of each of the diastereomeric S- and R-MTPA esters and (ii) comparative (Delta delta(SR)) analysis of the 1H NMR spectral data of these two esters. By analyzing the sign of the difference in chemical shifts for a number of analogous pairs of protons (the set of Delta delta(SR) values) in the diastereomeric esters (or amides), the absolute configuration of the original carbinol (or amino) stereocenter can be reliably deduced.
4.Quantitative and isomeric determination of amphetamine and methamphetamine from urine using a nonprotic elution solvent and R(-)-alpha-methoxy-alpha-trifluoromethylphenylacetic acid chloride derivatization.
Holler JM1, Vorce SP, Bosy TZ, Jacobs A. J Anal Toxicol. 2005 Oct;29(7):652-7.
Forensic Urine Drug Testing Laboratories often requires two confirmatory methods for a methamphetamine positive screen. First, methamphetamine is identified and quantitated using gas chromatography-mass spectrometry. If the total methamphetamine concentration is above the administrative cutoff level, the isomeric composition must be determined. This eliminates a possible contribution by over-the-counter cold medications that contain l-methamphetamine (Vick's inhalers). Products that contain only the l-isomer of methamphetamine must be distinguishable from prescription or illicitly manufactured methamphetamine, which consists mainly of the d-isomer. Optically impure derivatizing reagents will produce an impure mixture from a pure isomeric compound. Therefore, methods utilizing impure reagents can prove problematic when interpreting results. Use of an optically pure chiral derivatizing reagent, such as R(-)-alpha-methoxy-alpha-trifluoromethylphenylacetic acid chloride, allows for the creation and measurement of chromatographically separable isomeric compounds.