Abstract
Warming of l-α-santonin (Ia) with dimethylformamide in which is dissolved hydrogen halide results in cis-reversion of the lactone ring and l-6β-hydroxy-3-oxoeu-santona-1, 4-dienic lactone (VIIIa), or l-santonin C is formed. In this reaction, a linear-conjugated dienone compound (IXa), formed by the shift of the double bond, and l-α-desmotroposantonin (Va) are produced as by-products, as well as a compound assumed to be the trienone (Xa), with an increase of one double bond. These new rearrangement reactions also proceed similarly in racemic compounds and rac-santonin C (VIIIb) is formed from rac-α-santonin (Ib), and rac-santonin D (XII) from rac-β-santonin (XI).
