Hofmann Degradations of Tetrahydrosecurinine and Tetrahydrosecurininol. Stereochemistry at C-3a of Tetrahydrosecurinine

Abstract

The Hofmann degradations of tetrahydrosecurinine (II) and tetrahydrosecurininol (III) resulted in N-C_5a ring opening. The former gave two products, a normal methine base (VII) and an abnormal product (VIII), and the latter gave a normal methine base (XIII) alone. These products, (VII), (VIII), and (XIII), were interrelated as follows. Dehydration of VIII followed by hydrogenation gave an amino-lactone (IX), which was also prepared from VII by hydrogenation. On the other hand, lithium aluminum hydride reduction of VII gave XIII, which was converted to an amino-diol (XIV) by hydrogenation. The syntheses of the racemates of IX and XIV provided the proofs for their structures. The result establishes the configuration at C_3a of II.