Lycoctonine-type alkaloids

Structure Revisions and General Studies Revision of the Structures of Thirty-seven Lycoctonine-related Diterpenoid Alkaloids.—Lycoctonine was assigned structure (1) on the basis of an X-ray crystallographic analysis of (2) in 1956.4 Since that time, the structures of most of the lycoctonine-type alkaloids have been based on correlations with lycoctonine. 

This work, with the earlier report by Jones and Benn, has established a n.m.r. data base for the aconitine- and lycoctonine-type alkaloids which should greatly facilitate structural investigations of new bases in these series. 

The most important difference between an aconitine-type and a lycoctonine-type skeleton is that the latter contains an oxygenated functional group at C-7 whereas the former does not. The presence or absence of a ditertiary a-glycol system—either as its free hydroxyl or in its methylenated form—is thus the determining factor in the classification, as well as much of the chemistry, of the lycoctonine- and aconitine-type alkaloids, respectively. Two further trends are to be noted. All of the known lycoctonine-type alkaloids have had a (8-methoxyl at C-6 while in all of the aconitine-type alkaloids which contain a C-6 methoxyl, it is in the a-configuration. Also, whereas many of the aconitine-type alkaloids possess a bridgehead hydroxyl at C-13, none of the lycoctonine-type alkaloids have yet been isolated with a substituent of any kind at this position. 

These results may be explained by the steric hindrance offered by a C-6 a-methoxyl to the vulnerable C-19 methylene, thus preventing oxidation of the latter and thereby favoring attack on the iminoethyl group instead. The (3-oriented C-6 methoxyl of the lycoctonine-type alkaloids, however, offers no interferences with the C-19 methylene so... 

Acomonine.—Soviet researchers have reported the isolation of a new lycoctonine-type alkaloid, acomonine (6), which has no oxygen functionality at C-1. This base, C25H41NO7, m.p. 208—210 °C, was isolated from the roots of Aconitum monticola, co-occurring with songorine (7) and norsongorine (8). 

By analogy with other lycoctonine-type alkaloids, the remaining methoxy-group in deoxydelcorine was assigned to C-18. 

These diterpenoid alkaloids may be divided into two broad groups those based on a hexacyclic Cjp-skeleton, and those based on a C20-skeleton. The Ci9-alkaloids are commonly called aconitines, and all possess either the aconitine, the lycoctonine, or the heteratisine skeleton. Usually in the literature, the Ci9-diterpenoid alkaloids are referred to as either aconitine-type or lycoctonine-type alkaloids without structural differentiation. Because this practice sometimes creates confusion, we have divided the Ci9-diterpenoid alkaloids into three categories, defined as follows ... 

In 1969 Yunusov and his co-workers (143) reported on their mass spectral studies of aconitine- and lycoctonine-type alkaloids. On the basis of mass spectral analysis of isotalatizidine (61), condelphine (67), talatizamine (68), neoline (47), aconitine (4), aconine, lycoctonine (58), and some of their derivatives, they reported that the main ionization center in these alkaloids is the nitrogen atom. During the study of lycoctonine-type alkaloids, they observed that the base peak is usually derived by the loss of the C-l substituents as a radical. If a C-3 substituent was present, as in many of the aconitine-type alkaloids, the heteroring fragmented in a... 

In 1973, Waller and his colleagues (134,146) reported the mass spectral analysis of the lycoctonine-type alkaloids delcosine (163), acetyldelcosine (164), and delsoline (165). They mentioned that these alkaloids showed a similar fragmentation pathway. As an example, the mass spectrum of delcosine is discussed here. Waller and his group also studied the mass spectra of the tetramethylsilane (TMS) derivatives of delcosine, acetyldelcosine, and delsoline, and found that the results obtained were in agreement with the proposed fragmentation outlined for delcosine. 

Applications of N.M.R. Spectrometry to the C19 Diterpenoid Alkaloids 14-Acetylbrowniine.—A review of recent applications of carbon-13 n.m.r. spectrometry to the solution of some of the complex problems of C19 diterpenoid alkaloid chemistry has appeared. Using proton-decoupling techniques and additivity relationships, the carbon-13 chemical shifts for eighteen aconitine and lycoctonine-type alkaloids were assigned. Applications of these methods for the identification and structure elucidation of several new diterpenoid alkaloids were discussed. The new data presented in this work included the identification of... 

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