Diastereoselectivity Switch During Alkene Reductions: Diastereodivergent Syntheses of Molecular Fossils via MHAT or Homogeneous Catalytic Hydrogenation Reactions

Abstract

Sixteen geosterane derivatives were synthesized in up to 57 % overall yields in four steps harnessing the olefin cross‐metathesis (OCM) and Metal hydride H atom transfer (MHAT) or homogeneous hydrogenation reactions as key steps. Drawing on this strategy, the diastereomeric ratio (d. r.) reached up to 24 : 1 for the thermodynamic isomer and 7 : 1 for the other isomer in the hydrogenation step. In a geological sample from northeast Brazil, we confirmed the putative structures previously assumed as methyl 2‐(3α‐5αH‐cholestan) acetate, methyl 2‐(3β‐5αH‐cholestan)acetate, and methyl 6‐(3β‐5αH‐cholestan)hexanoate, as well three new molecular fossils of approximately 120 million years old. We also proved the migration marking ability of those carboxylic acids derived from forerunner geosteranes during an oil migration event, which suggests their aptitudes as molecular odometers. Our approach demonstrated swiftness and effectiveness in preparing a molecular library of geological biomarkers would also be appropriate to generate stereochemical diversity in molecular libraries for medicinal chemistry and natural product anticipation.

Mechanically accelerated catalytic hydrogenation: correlating physical state, reaction rate, and interface area

“…Herein, the selected gaseous reactant is molecular hydrogen, crucial in reducing unsaturated organic compounds to access simple scaffolds and complex molecular motifs like natural products and drugs. 13–22 Regarding hydrogen, there are a lot of concerns about how it is transported, stored, and used. Many regulations and safety measures need to be followed to ensure compliance with health regulations.…”