Trishomoallylic epoxidation

Asymmetric trishomoallylic epoxidation.1 The 6,7-double bond of 1 is epox-idized stereoselectively to afford 2 with trityl hydroperoxide catalyzed by (-)-diethyl tartrate and Ti(0-i-Pr)4 in the presence of molecular sieves. (-Butyl hydroperoxide is not useful in this case. The product was used for an enantioselective... 

Notable features concerning this work include the trishomoallylic epoxidation and the conversion of 78 to 80 by means of a PCC oxidation. The total synthesis proceeded in a total of 26 steps with 13 steps for the longest linear sequence. 

In Corey s total synthesis of the antiviral squalenoid venustatriol (71), three different asymmetric epoxidations were used (Scheme 9.8) [82]. Che-moselective epoxidation of the allylic alcohols in farnesol (65) and geraniol (69) [74] were carried out, along with the epoxidation of the trishomoallylic alcohol 67. The last of these proceeded with high diastereoselectivity in the presence of d-(-)-DET (47) and TrOOH as the oxidant [82]. 

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