Atisine isoatisine

It is based on a comparison of the the well-known atisine-isoatisine transknowledge that ajaconine forms an salt with mineral acids rather than an salt. C-nmr-spectral studies on ajaconine hydrogen-bonding solvents the ether linkage... 

The Sarett oxidation of atisine and isoatisine affords the conjugated enones atisinone (XLIV) and isoatisinone (XLV), respectively (23). Refluxing XLIV in methanol or ethanol effects a smooth isomerization to XLV, a reaction which parallels the facile atisine isoatisine isomerization (see Section V, A). The Sarett oxidation of atisine and isoatisine also gave rise to neutral by-products of interest (23). From atisine was obtained a compound assigned structure XVLI on the basis of spectroscopic evidence [v ax (Nujol) 3289, 3195, 3077, 1704, 1629, 1658 cm i Ash (EtOH) 228 mp. (e 7800) t9.05, 3H singlet (C—CH3), t4.12 and 4.84, 2H doublets (J =2 cps, C=CH2), t3.95, IH multiplet (-Nfl CO-)] and by... 

Atisine-Isoatisine Rearrangement. Further work has been presented by Pradhan and Girijavallabhan on the atisine (36) to isoatisine (37) rearrangement, which occurs on treatment with methanolic base. The n.m.r. spectrum of the reaction mixture in deuteriated solvent was examined at frequent intervals to... 

A. heterophyllum, in which atisine was the chief alkaloid, after standing four years, yielded 8 grams of isoatisine, due to isomerisation with heter-atisine. O 4 gm., and atisine hydrochloride, 0-35 gm. ... 

The isomerization of atisine to isoatisine and the conformational analysis of rings E and F of atisine, veatchine, and related alkaloids have been studied by n.m.r. spectroscopy. 12-O-Acetylnapelline is a new alkaloid which has been isolated from Aconitum karakolicum. 

The structure of atisinium chloride as 5 was confirmed recently by a single-crystal X-ray analysis (SO). The absolute configuration of atisinium chloride was determined as 45, 5S, 8/ , 10/ , 12/ , and 155 by Hamilton s method and confirmed by examination of sensitive Friedel pairs. A recent X-ray crystallographic study of isoatisine confirmed the assigned structure 75. The absolute configuration was established as 45, 55, 8/ , 10/ , 12/ , 155, and 195 for isoatisine. It is worth noting that isoatisine does not exist as a mixture of C-19 epimers. Early work on the chemistry of atisine and isoatisine... 

Dihydroatisine, a minor alkaloid of the roots of A. heterophyllum Wall, was isolated (SO) from the strong base fraction and its structure (78) was established by comparison with the sodium borohydride reduction product of atisine or isoatisine. Recently, an X-ray analysis of dihydroatisine confirmed (30) its structure and determined the absolute configuration as 45, 55, 87 , 107 , 127 , and 155. So far dihydroatisine has not been reported in any other plant. 

Vakognavine is the first example of an N, C-19-seco-diterpenoid alkaloid reported and an interesting alkaloid for biogenetic speculation. The authors (116) suggested that the C-19 aldehyde may be a plausible alternate to the pseudokobusine structure as an intermediate in the biosynthesis of the modified atisine-type skeletons such as hetisine. The C-19 hydroxyl of vakognavine hydriodide (119) is reminiscent of the oxazolidine oxygen of isoatisine. 

Among them five alkaloids and three flavonoid glycosides are known only from this plant while the rests are also reported from other plants. Gao et al. (2004) isolated and characterized six alkaloids (Figure 3) they are navirine (compound 1), isoatisine (2), hordenine (3), atisine (4), hetisinone (5) and delfissinol (6). Among them navirine (1) was reported as a new diterpenoid alkaloid while other five alkaloids are known in other plants too. Cao et al. (2008) reported two new C-20 alkaloids naviculine A (7) and B (8). Other terpenoid alkaloids were reported by our research group (Dall Acqua et al. 2008) they are navirine B (9), navirine C (10) and chellespontine (11). This latter one was previously isolated from aerial part of Consolida hellespontica (Desai et al., 1993). 

Early in their studies on the structure of atisine, Jacobs and Craig observed that brief treatment with warm alkali was sufficient to iso-merize atisine to another base named isoatisine 48). Subsequent work has shown that the related alkaloids veatchine 49), garryfoline 50), and... 

Since both atisine and isoatisine have tetragonal C-20 groups it is necessary to invoke factors in addition to the above equilibria to explain the greater stability of isoatisine over atisine. The following two interactions may be observed in Dreiding models of the atisine molecule ... 

Atisine hydrochloride (1 g.) in boiling methanol (40 ml.) containing sodium hydroxide (3 g.) for 3.5 hr. gives, on dilution and extraction with chloroform, isoatisine (almost quantitatively). 

Atisine, moreover, is a stronger base than are isoatisine and tetrahydroatisine, and it is probable, therefore, that at least one of the unsaturated centers is associated with the nitrogen atom in the weaker base, isoatisine, this center is assumed to have moved (2), as demonstrated in the part-formula (II). 

Oxidation of atisine (I) with an excess of alkaline permanganate at low temperature proceeds by a different route and affords a lactamdicarboxylic acid (V) (C21H29O6N) which is unsaturated, since, on hydrogenation, it readily absorbs one molar proportion of hydrogen. The dihydro acid (VI) is identical with the lactamdicarboxylic acid (VI) obtained analogously from isoatisine (II) and from oxoisoatisine (III) through dihydroxyoxoisoatisine... 

VII) both lactamdicarboxylic acids contain one tertiary carboxyl group and a primary hydroxyl group. This hydroxyl is attacked by further oxidation and two lactamtricarboxylic acids (VIII) and (IX) are obtained, from V and VI, respectively, or directly from atisine and isoatisine, respec-... 

Dehydrogenation of the saturated tricarboxylic acid (IX) gives 1,6-di-methylphenanthrene, whereas the characteristic product of dehydrogenation of atisine, tetrahydroatisine, and oxoisoatisine is 6-ethyl-l-methyl-phenanthrene. Since the lactamdicarboxylic acid (VI) derived from isoatisine also affords 1,6-dimethylphenanthrene, the 6-ethyl group must arise from a structural feature lost in the later oxidative stages. 

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