Proposed glabrescol

In their synthesis of the proposed glabrescol (90) (Scheme 3.30) [65], Kodama and coworkers reported that compound 88 was regio- and stereoselectively epoxidized at the central alkene with ketone 42 to give compound 89 after ring closure. The alkene inductively deactivated with the allylic acetate is less reactive. 

Corey and coworkers reported that (i )-2,3-dihydroxy-2,3-dihydrosqualene (104) was rapidly converted into proposed glabrescol 90 in 31% overall yield by enantio-selective pentaepoxidation with ketone 42 and subsequent cascade epoxide opening (Scheme 3.34) [69]. In their efforts to determine the correct stmcture of glabrescol, tetraene 106 was epoxidized with ketone 42. The resulting epoxide 107 was transformed into a chiral C2-symmetric pentacydic oxasqualenoid 109 (Scheme 3.35), which matches the reported isolated natural product glabrescol [70, 71]. 

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