Microbial stereodifferentiating reduction of 1,6-spiro[4.4]nonanedione, a gyrochiral diketone with two homotopic carbonyl groups

Article abstract of DOI:10.1021/jo00319a021

After a preliminary incubation of 1-spiro[4.4]nonanone (14) with Curvularia lunata, affording (+)-(1S)-alcohol 15 with 100% optical purity, (±)-1,6-spiro[4.4]nonanedione (8) was incubated with C. lunata for 8 h at 30°C to yield a 34:30:36 mixture of (-)-(5S)-8, (+)-trans-(5R,6S)-ketol 9, and (-)-cis-(5R,6R)-ketol 10 with respective 82%, 76%, and 6% optical purities. Incubation of (±)-trans-6-hydroxyspiro[4.4]nonan-1-one (9) furnished a metabolite mixture containing (-)-trans-(5S,6R)-9, (+)-trans,trans-(1S,5R,6S)-diol 11, and (+)-cis,trans-(1R,5S,6S)-diol 12 with respective 56%, 80%, and 73% optical purities. Although a modified quadrant rule for C₁ ketones could explain these microbial stereoselectivities, serious perturbing effects from the unique spirane framework and the neighboring functional groups were observed.