Further Withaphysalin Derivatives from Acnistus arborescens

Two new epimeric chlorinated withaphysalins, rel ‐(4 β ,5 β ,6 α ,18 S ,22 R )‐ and rel ‐(4 β ,5 β ,6 α ,18 R ,22 R )‐6‐chloro‐18,20‐epoxy‐18‐ethoxy‐4,5‐dihydroxy‐1‐oxowitha‐2,24‐diene‐26,22‐lactone ( 1 and 2 resp.), together with the new rel ‐(4 β ,5 β ,6 α ,18 R ,22 R )‐6‐chloro‐18,20‐epoxy‐4,5‐dihydroxy‐18‐methoxy‐1‐oxowitha‐2,24‐diene‐26,22‐lactone ( 3 ) and rel ‐(3 β ,4 β ,5 β ,6 β ,18 R ,22 R )‐5,6:18,20‐diepoxy‐3,18‐diethoxy‐4‐hydroxy‐1‐oxowith‐24‐ene‐26,22‐lactone ( 4 ) were isolated from the leaves of Acnistus arborescens and named withaphysalins T–W, respectively. The final structures and the complete 1 H‐ and 13 C‐NMR assignments of the three chlorowithaphysalins 1 – 3 were performed by means of HR‐ESI‐MS and 1D‐ and 2D‐NMR experiments, including COSY, HSQC, and HMBC, beside comparison with spectral data of analogous compounds from the literature. The structure of 4 was also confirmed by means of a single‐crystal X‐ray diffraction analysis.