Cytochrome P450 involved in the biosynthesis of the phytoalexin glyceollin. Stereospecific for (6aR,11aR)-3,9-dihydroxypterocarpan. (6aR,11aR)-3,9-dihydroxypterocarpan + O2 + reduced [NADPH--hemoprotein reductase] = (6aS,11aS)-3,6a,9-trihydroxypterocarpan + H(+) + H2O + oxidized [NADPH--hemoprotein reductase] Optimum pH is 7.4. Optimum temperature is 30 degrees Celsius. Up-regulated by methyl jasmonate, elicitor treatments and elicitor peptides GmSubPep, GmPEP890 and GmPEP914. Belongs to the cytochrome P450 family.