Secodaphnane-type Alkaloids

Two secodaphnane-type alkaloids (Figure 18.2), secodaphniphylline (8) [19,21,22] and methyl homosecodaphniphyllate (11) [19,21,22], were isolated by Yamamura and Hirata, and their structures were elucidated by X-ray analysis of methyl N-bromoa-cetyl homosecodaphniphyllate and chemical correlations between 8 and 11. The structures of the two related alkaloids, daphniteijsmine (9) [23] and daphniteijsma-nine (10) [24], were elucidated by spectroscopic analysis coupled with an exhaustive comparison of the NMR data of secodaphniphylline and methyl homosecodaphniphyllate (11). 

Biogenetically, daphtenidines A (84) and B (85) might be generated through an intermediate C from secodaphnane-type alkaloid B, followed by the formation of daphnilactone A (23) in Scheme 18.18 [85]. 

The distinct difference is that the C-IO-N linkage in daphniphylline-type alkaloids is broken and C-lO-C-7 bond is formed in secodaphnan-type alkaloids. No secodaphniphylline-type alkaloid has been obtained in recent years. 

Two new daphnezomine L-type alkaloids, daphnezomine L methyl ester (38), [26] and calycinumine B (39) [29], were reported (Figure 9). Daphnezomine L methyl ester (38) is structurally close to a hypothetical biogenetic intermediate between the secodaphnane and daphnane skeletons. Calycinumine B (39) features an imprecedented heteroatom-containing adamantane -like western hemisphere of daphnezomine L-type alkaloid. 

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