Aldolase-catalyzed synthesis of conformationally constrained iminocyclitols: preparation of polyhydroxylated benzopyrrolizidines and cyclohexapyrrolizidines.

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 rac-N-benzyloxycarbonylindoline-2-carbaldehyde as well as (2S*,3aS*,7aS*)- and (2S*,3aR*,7aR*)-N-benzyloxycarbonyloctahydroindole-2-carbaldehydes and a subsequent one-step catalytic deprotection-reductive amination.