Aldolase-Catalyzed Synthesis of Conformationally Constrained Iminocyclitols: Preparation of Polyhydroxylated Benzopyrrolizidines and Cyclohexapyrrolizidines

Abstract

A straightforward chemo-enzymatic synthesis of new polyhydroxylated benzo­pyrrolizidines and cyclo­hexa­pyrrolizidines is developed. The two-step strategy consists of l-fuculose-1-phosphate aldolase variant F131A-catalyzed aldol addition of dihydroxy­acetone phosphate to <i>rac</i>-<i>N</i>-benzyl­oxycarbonyl­indoline-2-carb­aldehyde as well as (2<i>S</i>*,3a<i>S</i>*,7a<i>S</i>*)- and (2<i>S</i>*,3a<i>R</i>*,7a<i>R</i>*)-<i>N</i>-benzyl­oxycarbonyl­octa­hydro­indole-2-carb­aldehydes and a subsequent one-step catalytic deprotection–reductive amination