Exploration of an epoxidation–ring-opening strategy for the synthesis of lyconadin A and discovery of an unexpected Payne rearrangement

• Brad M. Loertscher,
• Yu Zhang and
• Steven L. Castle

Beilstein J. Org. Chem. 2013, 9, 1179–1184, doi:10.3762/bjoc.9.132

• stereoselective sequence involving a Myers alkylation and a Shi epoxidation. Ring-opening of this epoxide with a vinylcopper complex afforded alcohol 26 instead of the expected product 27. An unusual Lewis acid promoted Payne rearrangement of an α-trityloxy epoxide is proposed to account for this outcome

• . Keywords: Lewis acid; lyconadin A; Myers alkylation; Payne rearrangement; Shi epoxidation; Introduction Lyconadin A (1, Figure 1) was isolated from the club moss Lycopodium complanatum in 2001 by Kobayashi and co-workers [1]. Subsequent to this discovery, lyconadins B–F were isolated and characterized [2

• , tentatively identified as alcohol 26, which had been produced in good yield. Presumably, the extremely hindered nature of internal epoxide 25 precluded its direct ring-opening, allowing alcohol 26 to form by means of a Payne rearrangement [30]. A possible mechanistic pathway for this transformation is given