Asymmetric allylation of carbonyl compounds: kinetic resolution of sec-allylboronates and total synthesis of natural products
2014-06-24T11:14:16Z (GMT) by
Asymmetric allylation of aldehydes with stoichiometric allylmetal reagents has evolved into an efficient and well established methodology for the synthesis of enantiomerically enriched homoallylic alcohols. The use of enantioenriched secondary allylboronates gives rise to a mixture of E/Z homoallylic alcohols with the opposite configuration at the stereogenic centre (reaction 1). The first part of this thesis presents a novel and conceptually different solution to attain high stereoselectivity in the allylation of aldehydes with secondary allylboronates. The method revolves around an efficient kinetic resolution of chiral racemic allylboronates (reaction 2). Catalysis by a chiral Brønsted acid ensures a face- and Z-selective allylation of aldehydes. This asymmetric allylation has proved successful over a wide range of aldehydes with different electronic and steric properties. The methodology provides a shortcut to enantio- and diastereomerically enriched homoallylic alcohols finding a wide use in pharmaceutical and fine chemicals development. The second part of the present thesis describes the asymmetric total synthesis of two bioactive metabolites of the Pseudopterogorgiane elisabethae family, ()-elisabethadione and ()-erogorgiane. Three key reactions steps to introduce the stereogenic centres in the natural product scaffold include asymmetric allylation, oxy-Cope rearrangement and cationic cyclisation.