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1.
J Org Chem ; 85(23): 15337-15346, 2020 12 04.
Article in English | MEDLINE | ID: mdl-33226804

ABSTRACT

An efficient, zirconium-catalyzed conversion of unprotected aldose sugars with acetylacetone to polyhydroxyalkyl furans or C-glycosylfurans is reported. The furan products are formed in up to 93% yield using 5-10 mol % ZrCl4. Pentoses are readily converted at room temperature, while hexoses and their oligosaccharides require mild heating (i.e., 50 °C). Efficient conversions of glycolaldehyde, glyceraldehyde, erythrose, a heptose, and glucosamine are also demonstrated. This approach outpaces each of the previous Lewis acid-catalyzed methods in at least one the following ways: (i) lower catalyst loadings; (ii) reduced reaction temperatures; (iii) shorter reaction times; (iv) equimolar substrate stoichiometry; (v) expanded sugar scope; (vi) higher selectivities; and (vii) the use of an Earth-abundant Zr catalyst.

2.
Anal Chem ; 89(12): 6399-6407, 2017 06 20.
Article in English | MEDLINE | ID: mdl-28505408

ABSTRACT

Liquid chromatography tandem mass spectrometry (LC-MS/MS), a widely used method for comparative 'omics analysis, experiences challenges with compound identification due to matrix effects, difficulty in separating isomer and isobaric ions, and long analysis times. Ion mobility spectrometry (IMS) has proven to be useful in separating isomer and isobar ions; however, IMS-MS suffers from decreased peak capacity due to the correlation in ion size and mass. In proof-of-principle experiments, the use of gas-phase hydrogen/deuterium exchange (HDX) combined with IMS-MS/MS techniques is demonstrated to offer advantages for compound identification. Measurements providing unique information for ions include m/z value, drift time in He buffer gas, drift time in He and D2O buffer gases, deuterium incorporation pattern (isotopic distribution), deuterium incorporation pattern after collisional activation, and fragment ion deuterium incorporation pattern upon collision-induced dissociation (CID). These techniques are here shown to be highly reproducible (drift time coefficients of variation < 1.0% and isotopic pattern root-mean-square deviations of 0.5-1.5%) while demonstrating an increased ability to distinguish individual molecules from diverse classes of compounds (peptides, catecholamines, nucleosides, amino acids, etc.). The concept of using such (and similar) information for rapid, high-throughput molecular identification via database searching of standard libraries is briefly discussed, and an example of such usage is presented for a bonafide metabolite extract sample.


Subject(s)
Amino Acids/analysis , Catecholamines/analysis , Deuterium Exchange Measurement , Isotope Labeling , Nucleosides/analysis , Peptides/analysis , Ion Mobility Spectrometry
3.
J Am Chem Soc ; 136(38): 13174-7, 2014 Sep 24.
Article in English | MEDLINE | ID: mdl-25184690

ABSTRACT

Gold-catalyzed oxidative cross-coupling of alkynes to unsymmetrical diynes has been achieved for the first time. A N,N-ligand (1,10-Phen) and PhI(OAc)2 were identified as crucial factors to promote this transformation, giving the desired cross-coupled conjugated diynes in excellent heteroselectivity (>10:1), in good to excellent yields, and with large substrate tolerability.


Subject(s)
Alkynes/chemistry , Diynes/chemistry , Gold/chemistry , Catalysis , Oxidation-Reduction
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