作者:Bruno Schönecker、Corinna Lange、Manuela Kötteritzsch、Wolfgang Günther、Jennie Weston、Ernst Anders、Helmar Görls
DOI:10.1021/jo000108x
日期:2000.9.1
The diastereomeric 16-bromo- and 16-azido-17-alcohols 5-8, 11, 12, 16, and 17 and 17-ketones 3, 4, 9, and 10 of the 13 alpha-estra-1,3,5(10)-triene series were synthesized as precursors for biologically active compounds and chiral Ligands for metal complexation. Conformational investigations of these and some other compounds via X-ray analysis and H-1 NMR spectroscopy show the existence of compounds with the classical steroid conformation (ring C chair, restricted conformation of ring D) and such with an atypical ring C twist-boat and a flexible ring D conformation. It could be shown that 17 beta-substituents or flattening of the D-ring are responsible for the twist-boat conformation, whereas compounds containing a 17 alpha-substituent or 17 keto group possess the classical conformation. By varying the substituents, compounds with either of these conformations can be intentionally synthesized. MO calculations confirmed the relative stability of the twist-boat conformation.