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Enantiomerically Pure Tribenzotriquinacenes through Stereoselective Synthesis
Wilko Greschner1, Beate Neumann1, Hans-Georg Stammler1
1Department of Chemistry, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld (Germany).
Abstract:
Inherently chiral acetophenones and benzaldehydes bearing the large, bowl-shaped framework of tribenzotriquinacene (TBTQ) were synthesized in enantiomerically pure form employing enzyme catalysis. Five-step sequences involving lipase CAL-B lead to the (M)-enantiomers, (+)-2-acetyl-TBTQ (M)-5 and (+)-2-formyl-TBTQ (M)-6, whereas use of lipase PS leads to the (P)-enantiomers, (-)-2-acetyl-TBTQ (P)-5 and (-)-2-formyl-TBTQ (P)-6, with at least 99% ee in each case. The absolute configuration of these rigid 3D building blocks was determined by X-ray diffraction analysis of the ketones 5 and by comparison of their chiroptical properties with those of the aldehydes 6.
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