Total Synthesis of Kalimantacin A

Easy and convenient millimole-scale synthesis of new, potential biomarkers for gamma-hydroxybutyric acid (GHB) intake - feasible for analytical laboratories

New biomarkers indicating the abuse of drugs and alcohol are still of major interest for clinical and forensic sciences. The endogenous neurotransmitter and approved drug, gamma-hydroxybutyric acid (GHB), is often illegally used for drug-facilitated crimes by spiking GHB into alcoholic beverages. Analytical detection windows of only 6 hours in blood and 12 hours in urine often too short to provide reliable proof of GHB ingestion. Therefore, new biomarkers are needed to prove exogenous GHB administration. Previously, amino-acid GHB conjugates were discovered in an untargeted metabolomics screening and fatty acid esters with GHB were recently discussed as promising biomarkers to enlarge the analytical detection time windows. However, the development of analytical methods is still slowed down since reference compounds for targeted screenings are still missing. In this paper, we describe simple procedures for the rapid synthesis and purification of amino acid-GHB conjugates as well as fatty acid esters, which can be adopted in analytical and clinical/forensic laboratories. Structural characterization data, together with IR, ¹ H-NMR, ¹³ C-NMR, high resolution mass spectra (MS), and MS/MS spectra in positive and negative ionization mode are reported for all obtained GHB-conjugates and GHB-conjugate precursors.

Modular terpene synthesis enabled by mild electrochemical couplings

The synthesis of terpenes is a large field of research that is woven deeply into the history of chemistry. Terpene biosynthesis is a case study of how the logic of a modular design can lead to diverse structures with unparalleled efficiency. This work leverages modern nickel-catalyzed electrochemical sp²-sp³ decarboxylative coupling reactions, enabled by silver nanoparticle-modified electrodes, to intuitively assemble terpene natural products and complex polyenes by using simple modular building blocks. The step change in efficiency of this approach is exemplified through the scalable preparation of 13 complex terpenes, which minimized protecting group manipulations, functional group interconversions, and redox fluctuations. The mechanistic aspects of the essential functionalized electrodes are studied in depth through a variety of spectroscopic and analytical techniques.

Total Synthesis of Thuggacin cmc-A and Its Structure Determination

The first total synthesis of thuggacin cmc-A and the determination of the absolute structure are described. The thuggacin family of antibiotics is of great interest due to the antibiotic activity against Mycobacterium tuberculosis. Based on the assumption that seven stereogenic centers in thuggacin cmc-A would share the same stereochemistry as thuggacin-A, all stereogenic centers of thuggacin cmc-A were strictly constructed in a stereocontrolled manner. The total synthesis allowed its stereostructure to be fully confirmed.