(22R)-20alpha,22-Dihydroxycholesterol is the second intermediate in th
e conversion of cholesterol to pregnenolone by cytochrome P450scc in s
teroidogenic tissues. We report a rapid method for the enzymatic synth
esis of (22R)-20alpha,22-dihydroxycholesterol from (22R)-22-hydroxycho
lesterol using mitochondria from the human placenta.