A 14 Parameter Study of UHPLC’s for Method Development Transfer and Troubleshooting

Five ultra-high pressure liquid chromatography (UHPLC) instruments were compared to one another by examining the overall system performance and key functions of the system parts including: pump, auto-sampler, thermo-stated column compartment, and the detector. The five UHPLC systems used in this study were: ThermoFisher Vanquish, Agilent 1290 Infinity I, Agilent 1290 Infinity II, Waters Acquity I-Class, and Shimadzu Nexera X2. The identities of the systems were blinded in the results and discussion section to use this study for scientific purposes only rather than for competition and marketing. The following tests were performed to evaluate and compare the five UHPLC systems: injector linearity and precision, sample carryover, sample (autosampler) temperature accuracy, column temperature accuracy and precision, pressure ripple, pump mixing accuracy, flow rate accuracy, detector drift and noise, detector linearity, wavelength accuracy, extra-column volume, and dwell volume determination. This study presents an approach on how to test the performance of UHPLC systems along with potential problems that analysts may face when using the UHPLC systems, examples of such issues are: retention time irreproducibility, low sensitivity, method transfer failure, etc.     

Asymmetric Total Synthesis of (−)‐Erogorgiaene and Its C‐11 Epimer and Investigation of Their Antimycobacterial Activity

A short, nine‐step, highly enantioselective synthesis of (?)‐erogorgiaene and its C‐11 epimer is reported. The key stereochemistry controlling steps involve catalytic asymmetric crotylation, anionic oxy‐Cope rearrangement and cationic cyclisation. (?)‐Erogorgiaene exhibited promising antitubercular activity against multidrug‐resistant strains of Mycobacterium tuberculosis.     

Beyond the Dimer and Trimer: Tetraspiro[2.1.25.1.29.1.213.13] hexadecane‐1,3,5,7‐tetraone—the Cyclic Tetramer of Carbonylcyclopropane

Tetraspiro[2.1.2⁵.1.2⁹.1.2¹³.1³]hexadecane‐1,3,5,7‐tetraone 4 , a unique tetraketone containing a cyclooctane core and four spiroannelated cyclopropane moieties, represents the previously unknown cyclotetramer of carbonylcyclopropane. For this purpose oxidation of the parent polyspirocyclic hydrocarbon was examined under various oxidative conditions, and the reactivity of oxidants towards methylene groups of the eight‐membered cycle, activated by adjacent spirocyclopropane rings, was evaluated and contrasted. Whereas the treatment of tetraspirohexadecane with ozone resulted in monooxidation, its reaction with methyl(trifluoromethyl)dioxirane afforded the product of four‐fold oxidation, triketoalcohol 10 . Subsequent oxidation of the latter with Dess–Martin periodinane gave the target tetraketone 4 .