Aporhoeadanes

The methoxybetaine (83), on treatment with aqueous acid followed by aerial oxidation in pyridine solution, is converted into the dioxoberberine (100). This can be converted by ammonium hydroxide in chloroform into aporhoeadane (101), which can be reduced with sodium borohydride and then converted into the enol acetate (102). When the imonium salt from (100) is allowed to stand in concentrated hydrochloric acid it is converted into the ether (103). ... 

Alternatively, treatment of oxybisberberine with pyridine hydrochloride in pyridine led to oxidative scission, and the nature of the products was dictated by the nucleophiles present and by the pH of the medium during the work-up. When the reaction was quenched with methanolic and aqueous acids, the products were the 8,13-dioxoberbines 44 and 45, respectively. These compounds undergo rapid, reversible, interconversion in acidic media through an immonium quinoid species. On the other hand, neutral work-up with buffered systems gives rise to the aporhoeadane 46, which is also produced rapidly but irreversibly on treatment of 45 with ammonium hydroxide. Alkaline work-up invariably produced as the major product Perkin s anhydroberberilic acid 47 as well as its solvolysis product noroxyhydrastinine (see Scheme 19.7). 

The benzazepinoisoindole 6, commonly referred to as Schopf Base VI, is prepared from commercially available jS-hydrastine, or by zinc in acetic acid reduction of berberinephenolbetaine. It can more conveniently be called an aporhoeadane derivative where the aporhoeadane nucleus is defined as in structure 5, the numbering system corresponding to that for the rhoeadines. 

In similar fashion, (—)-j8-hydrastine (23) is a source of the amino acid 24 which has been taken to the aporhoeadane 25 ... 

Thermal decomposition of narceine imide methiodide in the presence of 30% potassium hydroxide yields the Hofmann products 28 and 29, as well as the aporhoeadane derivative 30 which can be further reduced to 31 and 32 ... 

Turning back now to the aporhoeadane 32, basic pyrolysis of its methio-dide salt yielded three products in low yields, 34, 35, and 36. The cis cyclic olefin 34 was then treated with perbenzoic acid to furnish an A -oxide which upon reaction with aqueous mineral acid gave rise to 1 -methoxyallocryptopine ... 

A photochemical synthesis of benzazepines has allowed an alternate preparation of the aporhoeadane derivative 30, also known as Schopf Base VI. Compound 30 had originally been formed by reduction of berberinephenol-betaine with zinc in acetic acid (see Scheme 26.2). (For the chemistry of the aporhoeadane 30, see Sec. 23.1.2.)... 

Lithium aluminum hydride reduction of rhoeagenine is known to yield rhoeageninediol. Catalytic hydrogenolysis of rhoeageninediol diacetate leads to the expected substituted benzazepine 40 as well as to the aporhoeadane derivative 41. °... 

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