1.On treating -pregnatrien-3β,20-diol diacetate (Ⅴ) with potassium permanganate a hydroxylation product was obtained.Its structure has been assumed to be Ⅹ instead of Ⅵ as proposed previously.2.When the tetrol (Ⅷ) was treated with acetone-perchloric acid,it formed the acetonide ⅩⅡ,but not ⅩⅢ as reported in the literature.The latter was prepared from another route starting with Ⅵ.Based on these results we suspect the correctness of the assumption that 16α,17α,21-trihydroxy-20-keto steroids form 16,17-acetonides under the described conditions.