The efficient, 12-14 step (LLS) total synthesis of (-)-halenaquinone has been achieved. Key steps in the synthetic sequence include: (a) proline sulfonamide-catalyzed, Yamada-Otani reaction to establish the C6 all-carbon quaternary stereocenter, (b) multiple, novel palladium-mediated oxidative cyclizations to introduce the furan moiety, and (c) oxidative Bergman cyclization to form the final quinone ring.

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The efficient, 12-14 step (LLS) total synthesis of (À)-halenaquinone has been achieved. Keys teps in the synthetic sequence include:(a) proline sulfonamide-catalyzed, Yamada-Otani reaction to establish the C6 all-carbon quaternary stereocenter,( b) multiple,n ovel palladium-mediated oxidative cyclizations to introduce the furan moiety,a nd (c) oxidative Bergman cyclization to form the final quinone ring.

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Solid-contact ion-selective electrodes (ISEs) have the inherent advantage of being miniaturized in addition to maintaining high selectivity and sensitivity of the ionophore-based ISE. The major disadvantage of ISEs is the necessity of performing a calibration curve (varying the intercept in the linear calibration curve equation) each time before running experiments, which limits their application as one-time disposable sensors or for use in remote water sample analysis. To overcome these challenges, we designed a unique back contact made of 3,4-ethylenedioxythiophene (EDOT) and 4- (2,3-dihydrothieno[3,4-b][1,4]dioxin-2-ylmethoxy)-1-butanesulfonic acid, sodium salt (EDOT-S). The calibration-free ISEs showed near Nernstian responses of 57.2 ± 0.2 mV/log [K + ] and 28.5 ± 0.3 mV/log [Ca 2+ ], while maintaining their respective selectivity against major interfering ions. The detection limits for Ca 2+ and K + ISEs were 0.45 ± 0.01 and 1.68 ± 0.18 μM, respectively. The charging cycles of the PEDOT: PEDOT-S back contact allowed us to fix the background potential at a desired fixed intercept value across different ionophores (K + , Ca 2+ ). This protocol was used to determine the K + and Ca 2+ contents in creek water samples. The activity and concentration of [Ca 2+ ] and [K + ] in a local creek was found to be 257 ± 7.3 and 28.1 ± 1.1 μM, respectively.