3a-chloro-6, 7-secocholestane-6, 7-dioic acid anhydride (I). Windaus and Stein'reported that 3a-chloro-6, 7-secocholestane-6, 7-dioic acid (11) formed a crystalline anhydride melting at 187'. No further data on this compound were reported. A re-examination of this reaction produced a substance of the indicated melting point, the structure of which was, however, established to be 3a-chloro-B-norcoprostane-&one (111). Therefore, this ring closure ...
