Preparation and Exploitation of Versatile Cycloalkanoid Chiral Building Blocks

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Two cycloalkanoid chiral building blocks, one serving as the synthetic equivalent of chiral cyclopentadienone and the other serving as the synthetic equivalent of chiral cyclohexadienone, have been prepared in enantiomerically pure forms in both enantiomeric forms by employing either enzymatic or catalytic enantioselective reaction. Both of the building blocks carry a common bicyclo[2.2.1]octane background in their molecules which serve as the protecting group for one of the enone olefin functionality. At the same time, this protecting group brings about molecular bias allowing diastereocontrolled modification of the other enone moiety of both of the chiral building blocks and may be removed under thermolysis conditions to regenerate the olefin protected by extrusion of cyclopentadiene through a retro-Diels-Alder reaction.A variety of biologically active natural products, more than fifty, were synthesized enantio- and diastereo-controlled mannor from these building blocks by employing a variety of reactions, such as Claisen rearrangement, [2,3]-Witting rearrangement, tandem-Diels-Alder-ene reaction, Diels-Alder reaction, Fischer indolization, Bailis-Hillman reaction, Heck and Sonogashira reactions, etc, which occurred diastereoselectively from the convex-face of the chiral building blocks owing to the biased-framework of the chiral building blocks.