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Updated: Aug 24, 2026

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides
Published on: May 26, 2019
Conversion of squalene to the pentacarbocyclic hopene
Dirk J Reinert1, Gianni Balliano, Georg E Schulz
1Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstr. 21, D-79104 Freiburg, Germany.
Abstract:
The membrane protein squalene-hopene cyclase was cocrystallized with 2-azasqualene and analyzed by X-ray diffraction to 2.13 A resolution. The conformation of this close analog was clearly established, and it agreed with the common textbook presentation. The bound squalene undergoes only small conformational changes during the formation of rings A through D, thus requiring no intermediate. However, ring E formation is hindered by an entropic barrier, which may explain its absence in the steroids. The structure analysis revealed a mobile region between the active center cavity and the membrane, which may melt, opening a passage for squalene and hopene.
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