Palladium‐catalyzed synthesis of Benzoannulated spiroketal lactones derived from cholesterol: NMR characterization and crystal structures

Abstract

AbstractTwo new Benzoannulated spiroketal lactones were synthesized by Pd‐catalyzed cyclization of derivatives of 2‐(6‐hydroxyhex‐1‐yn‐1‐yl)benzoic acid obtained from cholesterol. Unexpectedly, the Pd‐catalyzed spirocyclization led to steroid isochromen‐1‐ones as major products and only small amounts of the expected spiroketal lactones. The obtained isochromen‐1‐ones were successfully converted to the desired spiroketal lactones by saponification followed by acidic workup. NMR characterization provided enough evidence on the structure of the obtained compounds. Single crystal x‐ray diffraction corroborated the proposed structures.