THE substitution of a hetero atom for a 2-methylene group in steroid hormones should lead to products useful in the elucidation of the mechanism of biological action of these compounds. While such a replacement is not expected to change the shape of the molecule and is compatible with the presence of the highly important 4,5 double bond, it alters considerably the chemical nature of carbon 3 (for example, replacement of the 2-methylene group by oxygen converts a 3-ketone to a lactone). A transformation of this type permits the study of the influence of the chemical reactivity of carbon 3 on the biological activity of the molecule. In 1956 experiments were initiated in this laboratory towards the preparation and the evaluation of this new and interesting class of compounds. When 1-androstene-3,17-dione (I) wds treated with 4 equivalents of lead tetraacetate in 90 per cent aqueous acetic acid 192 overnight at room temperature, and the resulting crude secoaldehyde-acid II reduced with aqueous sodium borohydride followed by acid treatment, there was obtained in about 50-60 per cent yield 178-hydroxy-2-oxaandrostane-3-one 3 (III),