Enantioselective total synthesis of some brevicomins using aldolase antibody 38C2

Aldolase antibody 38C2 (Aldrich no. 47,995-0) catalyzes the aldol reaction between hydroxyacetone and aldehyde 7 to give dihydroxyketone 8α in an enantiomeric excess (ee) >99%. This reaction has been performed on a semipreparative scale to give the product in 55% yield (ee = 98%). Aldol 8α can be converted to hydroxybrevicomins ent-5 and ent-6 by reduction and acid-catalyzed cyclization. Antibody 38C2 also catalyzes the retro-aldol reaction of racemic syn-8. After 52% conversion, the enantiomeric product (8β) is obtained in > 99% ee. By using either antibody-catalyzed aldol or retro-aldol reactions, both aldol enantiomers can be prepared with a single antibody catalyst. This methodology has been applied in highly enantioselective total syntheses of ten brevicomins.