Trifluoroacetic acid → 21-Hydroxy-17-(1-oxobutoxy)pregna-4,9(11)-diene-3,20-dione

Participants

Reaction Conditions

Reaction Steps

4 g (11.6 mM) of 17a,21-dihydroxy-pregna-4,9(11)-diene-3,20-dione were reacted with 20 mg of trifluoroacetic acid in 20 ml of dioxane and 10 ml of ethyl orthobutyrate for 5 hours at 100° C., and the low boiling head fraction was distilled off. The solution was cooled, then treated with 5 ml of a tartaric acid molar solution and heated to 40-50° C. for about 5 minutes to obtain 17α-butanoyloxy-21-hydroxy-pregna-4,9(11)-diene-3,20-dione. The solvent was evaporated off under vacuum and the residue was repeatedly taken up with dioxane. The resulting residue was dissolved in 200 ml of acetone and then 12 g trifluoroethyl octadecanoate (prepared from octadecanoyl chloride and trifluoroethanol), 20 g of Candida cylindracea lipase were added and the resulting suspension was stirred for 8-10 hours at 50° C., adding 2 g of C. cylindracea at regular time intervals. The lipase was filtered off, the filtrate was concentrated under vacuum and the residue was chromatographed on a silica gel column with a dichloromethane/methanol 98.5:1.5 mixture. The neat fraction was evaporated to obtain 4.9 g (7.17 mM) of 17α-butanoyloxy-21-octadecanoyloxy-pregna-4,9(11)-diene-3,20-dione.

Provenance & Evidence