12-Oxygenated pregnane derivatives. Part I. (a) 21-Acetoxy-12α : 17α-dihydroxypregn-4-ene-3 : 20-dione; (b) 12α : 21-diacetoxy-17α-hydroxypregn-4-ene-3 : 20-dione; (c) 3α : 12α : 21-triacetoxy-17α-hydroxypregnan-20-one; and (d) miscellaneous observations