Asymmetric synthesis of sultones and sulfonic acid derivatives
A highly efficient diastereo- and enantioselective route to alpha, gamma-substituted gamma-sultones via alpha-allylation of lithiated sulfonates bearing 1,2:5,6-di-O-isopropylidene-alpha-D-allofuranose as a chiral auxiliary has been developed. High asymmetric inductions of the alpha-allylations were achieved along with good to excellent yields. In all cases the diastereomerically pure allylated sulfonates could be obtained by recrystallization (de = 98%). Successive acid-catalyzed cleavage of the chiral auxiliary and subsequent diastereoselective ring closure of the sulfonic acid intermediates were accomplished following a one-pot procedure leading to the title compounds in good to excellent yields and excellent diastereo- and enantiomeric excesses (de, ee = 98%). The ring-opening reactions of these sultones were studied intensively with the purpose to develop an efficient asymmetric route to pharmacologically interesting sulfonic acid derivatives. In total, we have achieved facile and highly efficient enantioselective syntheses of alpha,gamma-substituted gamma-alkoxy, gamma-hydroxy and gamma-amino sulfonates in excellent diastereo- and enantiomeric excesses (de, ee = 98%) in all cases via ring-opening reaction of these gamma-sultones with alcohols, water and sodium azide, respectively as key steps. We have proven that the ring-opening of gamma-sultones proceeded via a SN2 mechanism with inversion of configuration at the attacked gamma-carbon atom. Furthermore, we have gained access to alpha, beta-substituted gamma-hydroxy and gamma-amino sulfonates in moderate yields with excellent diastereo- and enantiomeric excesses from chiral gamma-nitro sulfonates, which were synthesized via an asymmetric Michael addition of chiral lithiated sulfonates to nitroalkenes.
info:eu-repo/classification/ddc/540, Sultone, Alpha-Stellung, Gamma-Stellung, Sulfonsäurederivate, Asymmetrische Synthese, Ringöffnungsreaktion, Chemie, Asymmetric synthesis, sultones, sulfonates, allylation, ring-opening
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