• Cyclotetrasiloxane Frameworks for the Chemoenzymatic Synthesis of Oligoesters

      Zelisko, Paul M; Frampton, Mark B.; Jones, Tim RB (Royal Society of Chemistry, 2015-11-28)
      Immobilized lipase B from Candida antarctica (Novozym® 435, N435) was utilized as part of a chemoenzymatic strategy for the synthesis of branched polyesters based on a cyclotetrasiloxane core in the absence of solvent. Nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry were utilized to monitor the reactions between tetraester cyclotetrasiloxanes and aliphatic diols. The enzyme-mediated esterification reactions can achieve 65– 80% consumption of starting materials in 24–48 h. Longer reaction times, 72–96 h, resulted in the formation of cross-linked gel-like networks. Gel permeation chromatography of the polymers indicated that the masses were Mw ¼ 11 400, 13 100, and 19 400 g mol 1 for the substrate pairs of C7D4 ester/ octane-1,8-diol, C10D4 ester/pentane-1,5-diol and C10D4 ester/octane-1,8-diol respectively, after 48 h. Extending the polymerization for an additional 24 h with the C10D4 ester/octane-1,8-diol pair gave Mw ¼ 86 800 g mol 1. To the best of our knowledge this represents the first report using lipase catalysis to produce branched polymers that are built from a cyclotetrasiloxane core.
    • Information Seeking Behaviors, Attitudes, and Choices of Academic Chemists

      Taylor & Francis, 2018-04-09
      Chemists in academic institutions utilize a variety of resources and strategies to remain current and to track scholarly information, patents, and news. To explore how chemists in academic institutions remain current, librarians at four Canadian university institutions surveyed 231 and interviewed 14 chemistry faculty, staff, and graduate students on their information seeking behaviors and attitudes. According to survey results, a minority of chemists (13.9 percent) acknowledged that they were successfully keeping up to date, while 50.6 percent indicated that they were somewhat successful. However, a significant number of chemists (35.5 percent) indicated that they were unsuccessful and could do better in remaining current with information. Investigators analyzing focus group data identified three emergent themes related to remaining current: (1) there is “too much information – and not enough time.” No single information seeking strategy works; (2) “patents are important – but messy.” Chemists find themselves largely suspicious about the value and credibility of patents; and (3) chemists “could do better” in keeping up to date with new and emerging technologies. Chemists continue to be open to new tools and resources yet readily acknowledge that they are too often not sure which information seeking behaviors, resources, or strategies work best. This study helps to shed light on opportunities to identify and meet chemists’ evolving information needs.
    • Chemoenzymatic Approach to Tetrodotoxin: Synthesis of Fukuyama’s, Alonso’s, and Sato’s Advanced Intermediates

      Baidilov, Daler; Rycek, Lukas; Trant, John F.; Froese, Jordan; Murphy, Brennan; Hudlicky, Tomas (Wiley, 2018-05-11)
      The advanced intermediates in the syntheses of tetrodotoxin reported by Fukuyama, Alonso, and Sato were prepared. The key steps in the synthesis of the title compounds involved the toluene dioxygenase–mediated dihydroxylation of either iodobenzene or benzyl acetate. The resulting diene diols were transformed to Fukuyama’s intermediate in six steps, to Alonso’s intermediate in nine steps and to Sato’s intermediate in ten steps, respectively.
    • Isolation, Synthesis, and Semi-synthesis of Amaryllidaceae Constituents from Narcissus and Galanthus sp.: De novo Total Synthesis of 2-epi-Narciclasine.

      Borra, Suresh; Lapinskaite, Ringaile; Kempthorne, Christine; Liscombe, David; McNulty, James; Hudlicky, Tomas (ACS, 2018-05-22)
      An efficient protocol for the isolation of narciclasine from common Amaryllidaceae bulbs, separation from haemanthamine, and the occurrence of a trace alkaloid, 2-epi-narciclasine are reported. Attempts to convert natural narciclasine to its C-2 epimer by Mitsunobu inversion or oxidation/reduction sequences were compromised by rearrangement and aromatization processes, through which a synthesis of the alkaloid narciprimine was achieved. The methylation of the 7-hydroxy group of natural narciclasine followed by protection of the 3,4-diol function and oxidation/reduction sequence provided the target C-2 epimer. A de novo chemoenzymatic synthesis of 2-¬epi-narciclasine from m-dibromobenzene is also described. Haemanthamine and narciprimine were readily detected in the crude extracts of Narcissus and Galanthus bulbs containing narciclasine and the occurrence of 2-epi-narciclasine as a trace natural product in Galanthus sp. is reported for the first time.
    • Repetition of chemistry from a recently retracted paper. A cautionary note.

      Bedard, Korey; Ryan, Wilson; Baidilov, Daler; Tius, Marcus; Hudlicky, Tomas (Elsevier, 2018-06-20)
      The base-catalyzed condensation reaction between (E)-4-phenylbut-2-enal and phenylpropargyl aldehyde recently reported in the literature to provide formylcyclobutadiene was repeated under the published conditions. The product obtained was identified as (E)-5-phenyl-2-((E)-styryl)pent-2-en-4-ynal rather than the reported 2-phenyl-3-styrylcyclobutadiene-1-carboxaldehyde. The structure assignment is supported by NMR and IR data and a x-ray structure of the crystalline alcohol obtained by Luche reduction.
    • Preparation of Rearranged Allylic Isocyanates from the Reaction of Allylic Alcohols with 1-Cyano-4-dimethylaminopyridinium Bromide

      Baidilov, Daler; Makarova, Mariia; Rycek, Lukas; Hudlicky, Tomas (Thieme, 2018-10-11)
      A shorter and less costly alternative to Ichikawa’s [1,3]-transposition protocol for cyanates to isocyanates is described.
    • Chemoenzymatic Synthesis of the Antifungal Compound(–)-Pestynol by a Convergent, Sonogashira Construction of the Central Yne-Diene

      Borra, Suresh; Kumar, Manoj; McNulty, James; Baidilov, Daler; Hudlicky, Tomas (Wiley, 2018-10-19)
      A total synthesis of the fungal-derived natural prod-uct pestynol is reported via a convergent chemoenzymatic ap-proach from the readily available precursors geranyl bromide,ethyl acetoacetate, trimethylsilylacetylene, and bromobenzene. Synthetic (–)-pestynol proved to be identical in all respects to thenatural material, allowing confirmation of the structure includ-ing absolute stereochemistry.
    • A ‘green’ approach to fixing polyacrylamide gels

      Carbonara, Katrina; Coorssen, Jens R. (Elsevier, 2020)
      Handling chemicals that require specific safety precautions and protections generates the need for hazardous waste removal and transportation costs. With the growing effort to reduce both cost per analysis and the environmental footprint of research, we report an effective alternative to the widely used methanol/acetic acid gel fixation solution. 1.0 M citric acid dissolved in 5% acetic acid (C3A) provides comparable results following both SDS-PAGE and two-dimensional gel electrophoresis, while also eliminating waste removal costs. •Citric acid dissolved in acetic acid replaces current gel fixative solution.•Cost per analysis is reduced and hazardous waste removal costs eliminated.•Environmental footprint of research is reduced.
    • Sequential enzymatic and electrochemical functionalization of bromocyclohexadienediols: Application to the synthesis of (-)-conduritol C

      Hudlicky, Tomas; Goulart Stollmaier, Juana (Elsevier, 2020-02-14)
      cis-Diene diol obtained from the microbial oxidation of bromobenzene was used as a substrate for the chemoenzymatic acetylation and epoxidation with lipases. The model studies showed that the regiochemistry of the acetylation is solvent-dependent. The chemoenzymatic epoxidation followed the expected regiochemistry when compared to the chemical epoxidation with m-CPBA, but with the unexpected formation of bromoconduritol-C, an important intermediate whose electrochemical reduction led to the synthesis of (-)-conduritol-C. Experimental and spectral data are provided for all new compounds.