33 塩素化サントニンの立体構造

抄録

Many additional reaction derivatives of α-santonin (1) such as santonin dichloride (2), 2-chlorosantonin (3), santonin chlorohydrin (4), santonin α-epoxide (5), and santonin isochlorohydrin (6) have been reported. The stereochemical assignments of these known compounds were made by Hendrickson and Bogard. We synthesized several new santonin derivatives such as 4-methoxy-5-chloro santonin (7) and additional chlorination reaction products of the known compounds. During the stereochemical study of the new chlorinated santonin derivatives, we found it necessary to re-investigate structures of the compounds decided by Hendrickson and Bogard. We re-examined the structures of the known compounds mentioned above including new chlorinated santonin derivatives by X-ray crystallographic analyses. We could definitely decide their structures and revised their structure of santonin dichloride (2) to 1α,2β-dichlorosantonin (2') and santonin chlorohydrin (4) to 4α-hydroxy-5β-chlorosantonin (4'). From CD study of these compounds, it became clear that conformation of the compounds in solid are almost the same as in solution.