(16β,17α)-(+)-2-[3-(tert-butyldimethylsilyloxy)-16,17-dihydroxy-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phenanthren-17-yl]-6-methylheptan-3-one 3-ethylene ketal