16-.alpha.,17-dihydroxy-6-.alpha.-methylpregn-4-ene-3,20-dione, cyclic acetal with acetone 16-.alpha.,17-isopropylidenedioxy-6-.alpha.-methylprogesterone 19304-29-1 6-.alpha.-Methyl-16-.alpha.-17-[(1-methylethylidene)bis(oxy)]-pregn-4-ene-3,20-dione NSC56948 Pregn-4-ene-3,20-dione, 16.alpha.,17-(isopropylidenedioxy)-6.alpha.-methyl- Pregn-4-ene-3,20-dione, 6-methyl-16,17-[(1-methylethylidene)bis(oxy)]-, (6.alpha.,16.alpha.)- Progesterone, 16.alpha.,17-(isopropylidenedioxy)-6.alpha.-methyl-