Control of the stereochemistry of C14 hydroxyl during the total synthesis of withanolide E and physachenolide C

The stereochemical outcome of the epoxidation of Δ_14–15 cholestanes with mCPBA is controlled by the steric bulk of a C17 substituent. When the C17 is in the β configuration, the epoxide is formed in the α face, whereas if the C17 is trigonal (flat) or the substituent is in the α configuration, the epoxide is formed in the β face. The presence of a hydroxyl substituent at C20 does not influence the stereochemical outcome of the epoxidation.

The epoxide configuration in oxidation of C14–C15 alkenes is determined by the configuration of the C17 substituent.

Ten new withanolides from Physalis peruviana

Ten new withanolides, including four perulactone-type withanolides, perulactones E-H (1-4), three 28-hydroxy-withanolides, withaperuvins I-K (5-7), and three other withanolides, withaperuvins L-N (8-10), together with six known compounds (11-16) were isolated from the aerial parts of Physalis peruviana. The structures of these compounds were elucidated on the basis of extensive spectroscopic analyses (1D and 2D NMR, IR, HR-MS) and chemical methods.