A stereoselective synthesis of the tetracyclic quassinoid framework
Date
1993
Authors
Liu, Gang
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Abstract
A new synthetic route to the tetracyclic framework of the quassinoids, Compound 80, was developed. This new route, starting from 2-cyclohexene-1-one 41 via 2-bromo-1-vinylcyclohexenyl acetate il and (E,E)-6-(7-methoxycarbonyl-6-heptenylidene)-1-cyclohexene-1-carboxaldehyde 78 as intermediates, employed a diene-transmissive Diels-Alder cycloaddition as the key reaction and could be used for the total synthesis of quassinoid compounds. The formation of the ABD rings in the quassinoid skeleton was achieved in one step for the first time based on this new synthetic methodology.
The 8-lactone D ring formation with stereochemical control was investigated through the racemic (E)-3-methyl-6-propylidene-1-cyclohexene-1-carboxaldehyde 37 and (3S,4R)-(E)-6-propylidene-3,4-dihydroxy-O,O'-isopropylidene-1-cyclohexene-1-carboxaldehyde 39 using an inverse electron demand hetero Diels-Alder cycloaddition. The structures of the formed cycloadducts 38a and 40a revealed that the D ring formation could be stereochemically controlled by introducing a proper substituent at C-13 in the C ring.
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UN SDG 6: Clean Water and Sanitation