Naturally occurring steroidal lactones with a 17α-oriented side chain. Structure of withanolide E and related compounds

Four related steroidal lactones of the withanolide group possessing a 17α-oriented side chain have been characterised as (17S,20S,22R)-5β,6β-epoxy-14α,17,20-trihydroxy-1-oxowitha-2,24-dienolide [withanolide E (1)], (17S,20S,22R)-14α,l7,20-trihydroxy-1-oxowitha-2,5,24-trienolide [withanolide F (2)], (17S,20S,22R)-5α,6β,-14α,17,20-pentahydroxy-1-oxowitha-2,24-dienolide [withanolide S(3)], and (17R,20R,22R)-14α,17-dihydroxy-1-oxowitha-2,5,24-trienolide [withanolide P (4)]. The structure of withanolide E deduced here has been confirmed by X-ray analysis (reported elsewhere); those of withanolide F and S are related to that of withanolide E on the basis of common degradation products. The identification of withanolide P is based on spectral analysis.