Exploring Three Membered Rings: Synthesis, Opening, Rearrangements and Progress Towards the Synthesis of Morphine
Potential strategies toward the synthesis of rifampicin were investigated. Previous studies in the laboratory of Yamamoto described the rearrangement of terminal epoxy alcohols to yield silyl protected aldol products. The stereospecific synthesis of aldol products begin with the Horner-Wadsworth-Emmons olefination of an aldehyde followed by DIBAL reduction. The allylic alcohol was subjected to a Sharpless asymmetric epoxidation reaction. The epoxyalcohol was subjected to a Payne rearrangement followed by trapping with an aryl selenide. Using our developed methodology, we were able to synthesize a library of aryl selenyl diols. The addition of Meerwein salt to aryl selenides followed by base mediated cyclization provided epoxides for the Yamamoto rearrangement. The Yamamoto rearrangement provided aldol products in modest yield and may be used in the future for the synthesis of rifampicin.
Progress towards the synthesis of morphine is described via cyclopropyl ketone based intermediates. From simple lactones we were able to easily synthesize the starting material, aroyloxy arylketones in two to four steps. The ketones were then subjected to either Tsuji-Trost π-allyl chemistry followed base mediated cyclopropanation or simple base-mediated cyclopropanation, the former providing better yields. Upon addition of base, the starting aroyloxy arylketones exchange their aryl groups and generally provide two different cyclopropyl aryl ketones.