1. Spontaneous butenolide ring formation of pregnane-21-O-malonyl hemiesters under mild reaction conditions is facilitated by the 14β-hydroxy group present in all natural cardenolides. Issue 30 (28th July 2016) Authors: Pádua, R.M.; Meitinger, N.; Hennemann, M.; Schebitz, P.; Waibel, R.; Löber, S.; Gmeiner, P.; Clark, T.; Kreis, W. Journal: Tetrahedron Issue: Volume 72:Issue 30(2016) Page Start: 4556 Record Type: Journal Article View Content: Available online (eLD content is only available in our Reading Rooms) ↗