Allocryptopine synthesis

Bentley and Murray (201) reported another method for synthesis of protopine alkaloids allocryptopine (392) and cryptopalmatine (395) from tetrahydroprotoberberine /V-oxides (35a and 400) through oxidative rearrangement with potassium chromate (Scheme 73). 

Scheme 75. One-step synthesis of allocryptopine (392) from tetrahydroberberine methiodide (1) by photooxygenation. Reagents a, h, 02, Rose Bengal, MeOH. 

The synthesis of allocryptopine by Haworth and Perkin (82) was the first application of the process already outlined for cryptopine and protopine. This choice was made because the starting material, tetrahydro-berberine ((XXIX) with the methylenedioxy and the methoxy groups interchanged) was readily available. Furthermore, Pyman (18) had already made a full investigation of the decomposition of the methohydroxide to... 

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