An Approach to the Synthesis of Cancentrine

Cancentrine, isolated from Dicentra canadensis (Goldie) Walp. Fumaria-ceae), is a dimeric base composed of a cularine unit joined to a morphinane unit by an unusual spiro bridge (darkened section). Two naturally occurring dehydrocancentrines are also known, namely, the yellow dehydrocancentrine-A, which possesses a C-8,14 double bond, and dehydrocancentrine-B, which is unsaturated between C-31 and -32. Catalytic reduction of either of these dehydro bases using Adams catalyst yields cancentrine.  

In a model study, suggested by a proposed biogenetic scheme for cancen-trine, 3,4-dihydropapaverine was condensed with 1,2-cyclohexanedione in the presence of Triton B and pyridine to afford the spiro compound 5 in good yield  

The CMR chemical shifts for cularine are indicated in the structure below.  

Kametani, K. Fukumoto, and M. Fujihara, Chem. Pharm. Bull., Tokyo, 20, 1800 (1972). 

Shamma, The Isoquinoline Alkaloids, Academic Press, New York (1972), p. 153 ff. 

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