Pyrrole, Imidazole, Pyrrolizidine, Pyridine, and Related Alkaloids

5 Pyrrole, Imidazole, Pyrrolizidine, Pyridine, and Related Alkaloids 

The alkaloids remaining to be described at this point have been grouped together for convenience although they are, to our minds as spectroscopists, unrelated. 

Oxalicine A. An interesting pyridine-containing alkaloid, oxalicine-A (25), was communicated in 1989 (Ubillas et al. 1989). The communication referred to the HMQC experiment but cited the HMBC reference of Bax and Summers (1986). Unfortunately, no details of any long-range connectivities were communicated and, to the best of our knowledge, have not been reported elsewhere. 

Mikimopine. The alkaloid mikimopine (26), induced by Agrobacterium rhizogenes, was isolated from the hairy roots of tobacco (Isogai et al. 1990). On treatment with acid, the alkaloid underwent dehydration to afford the corresponding y-lactam, which was characterized using connectivities from an HMBC spectrum. Connectivities observed are shown on the structure. 

Curassanecine, In a synthetic study, Gramain et al. (1991) report the preparation of both natural curassencine (27, stereochemistry shown) and its 1-epimer. This communication is interesting because both Jch couplings were observed in the naturally occurring alkaloid from the H2 methylene protons to Cl, but only a correlation from the upheld H2 methylene proton to Cl was observed in the case of the 1-epimer. Ultimately, the stereochemistry 

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