Four related steroidal lactones of the withanolide group possessing a 1 7a-oriented side chain have been characterised as (1 7S.20S.22R) -5~,6~-epoxy-l4a,l7,20-trihydroxy-l -oxowitha-2,24-dienolide [withanolide E (1 )],(1 7S,20S.22R)-14a,l7,20-trihydroxy-l -oxowitha-2.5.24-trienolide [withanolide F (2)], (1 7S,20S,22R)-5a,6P,-14a.17.20-pentahydroxy-1 -oxowitha-2.24-dienolide [withanolide S (3)], and (1 7R,20R,22R)-14a,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.
Rehovot, IsraelWE have briefly reported the isolation of withanolides E (1) and F (2), two steroidal lactones of the withanolide group, characterised by the unusual a-orientation of the side chain.1 The structure of withanolide E (1) was unequivocally determined by crystallographic analysis,l as (1 7S,20S,22R) -5 p,6@-epoxy-14a, 17,20-trihydroxy-1oxowitha-2,24-dienolide , with a boat-like conformation for ring A, a distorted half chair for ring B, and a normal chair for ring c; ring D has an envelope form in which C( 14) is out-of-plane. The compound crystallises with two molecules of water; the C( 14) and C(20) hydroxygroups are hydrogen bonded. As a result, the 17p-OH . C(13)Me and 17p-OH . '22-H distances are decreased, and the 20a-OH --C(13)Me distance is
