Enantioselective synthesis of heliannuols. A: (+)-heliannuol A and (-)-heliannuol D. B: (-)-heliannuol D.

Recently, we have published a high yield route to (±)-heliannuol D16 based on biomimetic considerations. The synthesis starts with the readily available 2- 113 -

methyl-hydroquinone 41; acetylation and Fries rearrangement (42), followed by Grignard chain elongation and epoxidation with m-CPBA lead to the two possible diastereoisomers 43 and 44. The key step in the synthesis is the basic-catalyzed epoxide ring opening etherification that yields both possible diastereoisomers (±)-heliannuol D and 45 with an overall yield of 60.7 % for the whole process (Fig. 5.7).

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