Yuzurimine-type alkaloids

Biogenetically, daphnilactone-B (36) is regarded as a plausible intermediate between daphniphylline-type and yuzurimine-type alkaloids. Thus, daphnilactone-B (36) was converted to a daphniphylline-type compound (38, mp 166-168° C22H3302N) via a bromocyanamide [39, mp (dec) 210°] and a debromocyanamide (40, mp 208-212°), as shown in Scheme V. The structure of this daphniphylline-type compound 38 was confirmed by its mass, IR, and NMR spectra coupled with von Braun degradation of 38 leading to the formation of a new... 

Daphnezomines C (39) and D (40), possess the secodaphniphylline-type skeleton with a nitrone functionality, while daphnezomine E (41) is the first N-oxide of a daphniphylline-type alkaloid, though the N-oxides of several yuzurimine-type alkaloids have been reported [45]. 

Calyciphylline A-type alkaloids are a group of rare C-22 fiised hexacyclic nor-Daphniphyllum alkaloids, biosynthesized by the fission of C-l-N bond of yuzurimine-type alkaloid and the formation of a new bond between C-4 and nitrogen. Calyciphylline A-type alkaloids possess a 6/5/5/7/5/6-membered ring system and an oxo group on C-1. 

The structures, including relative stereochemistry, of daphnezomines H (44), I (4S), J (46), and K (47), four new alkaloids possessing a daphnilactone-type (44 and 4S) or a yuzurimine-type skeleton (46 and 47) were elucidated on the basis of spectroscopic data [47]. Daphnezomine I is the first N-oxide alkaloid having a daphnilactone-type skeleton, while daphnezomine J is the first alkaloid possessing a yuzurimine-type skeleton with an anti-Bredt-rule imine [57,58]. 

From a structural point of view, the 38 alkaloids so far obtained from the Daphniphyllaceae are classified into six types of nitrogen heterocyclic skeleton represented by daphniphylline (1), secodaphniphylline (2), daphnilactone-A (3), daphnilactone-B (4), yuzurimine (5), and daphnigracine (6), as shown in Fig. 1. Of the alkaloids, the 9 daphnigracine-type alkaloids are distinct from the other types in the following point they have no 2-azabicyclo[3.3. l]nonane ring system in their structure. 

Daphnilactone B type alkaloids are a small group of C-14,15-seeo-yuzurimines. Most of them form a laetone between the carbonyl at C-22 and the hydroxy attached to C-21. 

This group of alkaloids is biogenetically originated from yuzurimine and daphnilactone type alkaloids by cleavage of the C-6-C-7 bond. All of them have a tetracyclic ring system comprising an octahydroindole and a hexahydroazulene rings. 

Calyciphylline B type alkaloids are a group of rare C22 fused-pentacyclie yuzurimine type nor-Daphniphyllum alkaloids. Most of them eontain a six-member laetone ring. A new ealyciphylline B type alkaloid, daphlongamines H (51) was reported (Figure 13) [45]. 

The reaction was most successful using hydroxylamine, and when the dipolarophile was an imsaturated ester, subsequent reduction of the N-0 bond and cyclization to the lactam provided the core ring system of the yuzurimine, daphnilactone B, and bukittinggine type Daphniphyllmn alkaloids [55], Asymmetric construction of rings A-D of Daphnicyclidin-Type alkaloids was reported [56],... 

Coldham et al. reported on a cascade reaction sequences involving condensation, cyclization, intramolecular dipolar cycloaddition for preparation of fused tricyclic heterocycles which can be converted in two steps to a 1,3-oxazine present in some yuzurimine-type Daphniphyllum alkaloids under some conditions [57], In another study, addition of hydroxylamine to substituted 4-chlorobutanals gives intermediate nitrones that imdergo tandem cyclization and then intramolecular dipolar cycloaddition to give the core... 

Coldham, L. Watson, H. Adams, N. G. Martin, Synthesis of the core ring system of the yuzurimine-type Daphniphyllum alkaloids by cascade condensation, cyclization, cycloaddition chemistry, J. Org. Chem. 76 (2011) 2360-2366. 

Numerous UCNMR investigations on alkaloids have been reported in the literature [598, 599]. In Table 5.13 the 13C chemical shifts and structures of representative alkaloids of different types are collected Pyrrolidine, piperidine and pyridine [600-602], tropane [600, 603-605], izidine [606-612], indole [600, 603, 613-633], isoquinoline [599, 630, 634-647], quinolinic [648-656], imidazole [657], yuzurimine alkaloids [658], alkaloids with exocyclic nitrogen [659, 660], diterpenoid [661-663], steroid [664-666] and peptide alkaloids [667-671], The complete signal assignment for the alkaloids given in Table 5.13 was achieved using the correlations between 13C NMR spectral parameters and structural properties and the 13C chemical shift values of model compounds described in Chapters 3 and 4 of this monograph. 

From a structural viewpoint, these alkaloids are mainly divided into five types of nitrogen heterocyclic skeletons represented by daphniphylline (I), secodaphniphylline (28), daphnilactone-A (34), daphnil-actone-B (36), and yuzurimine (43). In this chapter, all of these alkaloids will be described including their spectral and chemical properties. Biogenesis of these bases with complex structure is quite interesting... 

The structure of yuzurimine (XLVII) had already been shown to be of a different type from that of daphniphylline and the isolation of two more alkaloids was reported (73). Yuzurimine A, C25H35O5N (hydrochloride, mp 249°-252°), was shown to be desacetoxyyuzurimine (XLVIII) by... 

X-ray crystallographic determination utilizing direct phasing methods. Although this compound contains the 2-azabicyclo[3,3,l]nonane ring system common to all of the Daphniphyllum alkaloids, it represents another new structural type. It is possibly related to yuzurimine (61) by formation of a C-8—C-22 bond and double-bond migration from C-8—C-9 to C-8—C-12. 

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