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2006

November 24, 2006

Building Addressable Libraries: The Use of a Mass Spectrometry Cleavable Linker for Monitoring Reactions on a Microelectrode Array

Ceng Chen, Gabriella Nagy, Amy V. Walker, Karl Maurer, Andy McShea, and Kevin D. Moeller
J. Am. Chem. Soc., 2006, 128 (50), 16020–16021

Time-of-flight secondary ion mass spectrometry (TOF SIMS) has been used in conjunction with a mass spectrometry cleavable linker to determine the percent conversion of reactions that were conducted site-selectively on an addressable microelectrode array. When combined with fluorescence techniques for analysis of the reactions, the TOF SIMS experiment provides a means for optimization of both reaction confinement and reaction efficiency on the microelectrode arrays.

 

October 15, 2006

Oxidative Cyclizations and the Synthesis of Lactones: A Streamlined Synthesis of epi-Crobarbatic Acid

John D. Brandt and Kevin D. Moeller
Heterocycles 2006, 67, 621-628

While anodic cyclizations have been shown to be compatible with the synthesis of lactones, the previous synthetic route to the starting materials was cumbersome and limited the overall utility of the approach. In this manuscript, a new strategy is reported that allows for very rapid synthesis of the electrolysis substrates. In addition, an efficient conversion of the ortho ester product obtained from the oxidative cyclization to a lactone acid is reported. The result is a dramatically improved synthetic strategy for the synthesis of functionalized tetrahydrofuranones.

 

October 3, 2006

Building Functionalized Peptidomimetics: Use of Electroauxiliaries for Introducing N-Acyliminium Ions into Peptides

Haizhou Sun, Connor Martin, David Kesselring, Rebecca Keller, and Kevin D. Moeller
J. Am. Chem. Soc., 2006, 128 (42), 13761–13771

A series of silyl-substituted amino acids have been synthesized, inserted into peptides, and then employed as precursors for oxidatively generating reactive N-acyliminium ions. Both electrochemical and chemical oxidation procedures have been employed. N-Acyliminium ion generation in a solid-phase substrate as well as application to a small library of functionalized dipeptides has been demonstrated. Limitations in terms of how electron-rich the silyl groups can be as well as the compatibility of multiple silyl groups within a longer peptide are defined.

 

May 4, 2006

Anodic cyclization reactions: probing the chemistry of N,O-ketene acetal derived radical cations

Yung-tzung Huang and Kevin D. Moeller
Tetrahedron, 2006, 62(27), 6536-6550

The chemical reactivity of radical cations derived from N,O-ketene acetals has been examined and compared with the reactivity of radical cations derived from both ketene dithioacetals and enol ethers. Synthetically, the N,O-ketene acetal radical cations lead to more efficient cyclization reactions than either the ketene dithioacetal or enol ether derived radical cations. Cyclic voltammetry experiments using allylsilane trapping groups show that the efficiency of these cyclizations is not due to the N,O-ketene acetal radical cations being more reactive but rather more stable to decomposition. Finally, cyclizations using chiral oxizolidinones were examined.

 

January 28, 2006

Building Addressable Libraries: Site Selective Coumarin Synthesis and the “Real-Time” Signaling of Antibody−Coumarin Binding

Eden Tesfu, Kris Roth, Karl Maurer, and Kevin D. Moeller
Org. Lett., 2006, 8 (4), 709–712

The feasibility of using active semiconductor chips containing addressable arrays of microelectrodes for the “real-time” monitoring of biologically relevant binding events has been demonstrated by detecting the binding of a coumarin substrate by an anticoumarin antibody. The coumarin substrate was synthesized proximal to predetermined electrodes on the chip with the use of a Pd(II) reagent that was itself generated by using the selected electrodes. Once the coumarin was synthesized, its binding to the anticoumarin antibody was detected by monitoring the current associated with a ferrocene−ferrocinium ion redox cycle that was established between the electrodes on the chip and a remote auxiliary electrode.

 

December 13, 2005

Building Addressable Libraries: Spatially Isolated, Chip-Based Reductive Amination Reactions

Eden Tesfu, Karl Maurer, and Kevin D. Moeller

J. Am. Chem. Soc., 2006, 128 (1),  70–71

Pd(II) reagent has been generated at preselected sites on an electrochemically addressable chip and used to effect the oxidation of the neighboring alcohols on the polymer coating the chip’s surface. The resulting carbonyls were then used to accomplish site-selective reductive amination reactions on the chips. The work demonstrates that the confinement strategy developed for spatially isolated Wacker oxidations to specific sites on the chips is general and can be used for other Pd(II)-based reactions.
 
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