Daphnilactone B-type alkaloids

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. 

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... 

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]. 

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. 

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],... 

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... 

Tetracyclization. The Heathcock group1 has described a remarkably short and efficient synthesis of the skeleton of Daphniphyllum alkaloids (2) by reaction of the dialdehyde 1 with gaseous ammonia and then dissolution in acetic acid at 70°. The yield is 77%, based on the diol precursor to 1. The azadiene a and the imine b have both been isolated and identified. The conversion of a to b is an intramolecular Diels-Alder type reaction. The tetracyclization may well be involved in the biosynthesis of alkaloids such as Daphnilactone A (3). 

---