Lycodine-type alkaloids

Phlegmarine-type alkaloids possess a C16N2 skeleton that consists of a piperidine ring and a (decahydro)quinoline ring that are connected via a methylene group (Scheme 10). They might be the biogenetic intermediates of lycodine (49) We next describe the structure elucidation of this new class of alkaloids based on asymmetric total syntheses. 

Complanadine A (43) is the first dimeric alkaloid containing a lycodine-type C16N2 skeleton among the many Lycopodium alkaloids reported so far. 

The absolute configuration of lycopodine (18) has been confirmed by an X-ray crystallographic study of the hydrochloride. The Cn.m.r. spectra of several alkaloids of the lycopodine (19) and lycodine (22) type have been studied and the resonances assigned. Of particular interest is the finding that the N-methyl group in the obscurines and N-methyl-lycodine (22) prefers the axial configuration. 

Lycodine and its related alkaloids as the numbering system implies are closely related to the lycopodine type. Selagine is but a minor variant of the general scheme in which the C-9 carbon derived from an acetate carboxyl has been lo.st in the elaboration of the system. 

Lyconadin A (44) is a novel type of alkaloid consisting of five fused rings (one 5-membered and four 6-membered rings), while alkaloid 45 is the first lycodine analog with a hydroxy group at C-11 (37). A plausible biogenetic path for 44 and 45 is shown in Scheme 9 (37). Both alkaloids may be derived from L-lysine via pelletierine, followed by further cyclization of the phlegmarine skeleton (74,77). 

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