Regioselective Functionalization of the Oxazole Scaffold Using TMP-Bases of Mg and Zn

A general method for the synthesis of 2,4,5-trisubstituted oxazoles has been developed. Starting from commercially available oxazole, successive metalations using TMPMgCl·LiCl or TMPZnCl·LiCl led to the corresponding magnesiated or zincated species which were stable toward ring fragmentation. Furthermore, they readily reacted with various electrophiles, such as aryl and allylic halides, acid chlorides, TMSCl, and TMS-CN, providing highly functionalized oxazoles

GreA and GreB proteins revive backtracked RNA polymerase in vivo by promoting transcript trimming

The GreA and GreB proteins of Escherichia coli show a multitude of effects on transcription elongation in vitro, yet their physiological functions are poorly understood. Here, we investigated whether and how these factors influence lateral oscillations of RNA polymerase (RNAP) in vivo, observed at a protein readblock. When RNAP is stalled within an (ATC/TAG)(n) sequence, it appears to oscillate between an upstream and a downstream position on the template, 3 bp apart, with concomitant trimming of the transcript 3′ terminus and its re-synthesis. Using a set of mutant E.coli strains, we show that the presence of GreA or GreB in the cell is essential to induce this trimming. We show further that in contrast to a ternary complex that is stabilized at the downstream position, the oscillating complex relies heavily on the GreA/GreB-induced ‘cleavage-and-restart’ process to become catalytically competent. Clearly, by promoting transcript shortening and re-alignment of the catalytic register, the Gre factors function in vivo to rescue RNAP from being arrested at template positions where the lateral stability of the ternary complex is impaired

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

In this review we summarize the most important procedures for the preparation of functionalized organzinc and organomagnesium reagents. In addition, new methods for the preparation of polyfunctional aryl- and heteroaryl zinc- and magnesium compounds, as well as new Pd-catalyzed cross-coupling reactions, are reported herein. Experimental details are given for the most important reactions in the Supporting Information File 1 of this article