Lycopodium Alkaloids: Xvi. Annotine

Abstract

Annotine, C~J I~I O~N , is shown to be pentacyclic and to contain a tertiary hydroxyl group, a lactone function, a tertiary nitrogen atom, and a dialkylated double bond. The position of the double bond and the tertiary hydroxyl group relative t o the nitrogen atom has been established by Emde degradation of annotine methiodide. The presence of a lactone function is inferred from the reduction of annotine to dihydroannotinol, a hemiacetal, which reacts with 1 mole of ethyl mercaptan. T h e reduction of the lactone to a diol in a n annotine derivative has been carried out. T h e chemical studies and the examination of annotine and its derivatives by modern instrumental methods allow the assignment of a plausible structure to the alkaloid.Annotine, C16H2103N (I), was first isolated from L. annotinz~m of Canadian origin by hiIanslte and Marion and designated alkaloid L . l l (1). I t was subsequently found in European plant material by Bertho and Stoll (2), who assigned the name annotine t o it, and by Achmatowicz and Rodewald (3). An examination of the functional groups of annotine was carried out by Perry and MacLean (4), who concluded that the alltaloid contained a tertiary nitrogen atom, a double bond, a hydroxyl group, a ketonic carbonyl group, and a third inert oxygen function, which they ascribed t o a n ether linkage other than an epoxide.In this coinmunication we wish t o report further studies on annotine by chemical and modern instrumental methods. These studies have shown that annotine is a lactone and have thereby established the nature of the third inert oxygen function. They have also allowed a n assignment of the position of the double bond and the hydroxyl group in the n~olecule relative t o the nitrogen atom and have led t o the development of a plausible structure for the molecule.Nuclear magnetic resonance (n.m.r.) spectroscopy has been used extensively in this study and has provided useful information about the functional groups and their environment in annotine and its derivatives. The n.m.r. spectrum of annotine has a quartet centered a t T = 4.04 (J = 10 c.p.s.) with a n intensity corresponding to two protons. This H\ band indicates the presence of the grouping /C=C\ and is an example of an intermediate case of an AB spectrum in which the chemical shift between the two nuclei is comparable to the coupling constant between them (5). I t was possible t o resolve each component of the quartet into a triplet in each of which the splitting was the same. These data indicate the presence of a methylene group adjacent to the double bond, as in theA singlet occurring a t T = 8.57 with an intensity corresponding to three protons points to the presence of a methyl group attached t o a quaternary carbon. The low T value of the C-methyl group in this system can possibly be explained by the deshielding effect of a carbonyl group beta t o the methyl protons. I t has been postulated that the deshielding effect in such a system is due to the anisotropy of the carbonyl group and that the deshielding e...

Lycopodium Alkaloids: Xvii. Mass Spectra of Annotine and Some Annotine Derivatives

“…T h e peak a t m/e 123 is actually a quartet and thus not a s important in the overall fragmentatioil a s the examination of the low-resolution spectrum alone infers. -'The infrared spectrum of dihydroannotinol (1) shona that the compound in the solid state as \\.ell as in solution exists in a hemiacetal form. In the ion source of the mass spectrometer, however, dihydroannotinol is present in the gaseous phase, and may exist in both the hemiacetal and the hydroxy aldehyde forms as shown below.…”

“…The compo~inds used in this investigation Tere prepared according to methods described in a previous paper in this series (1).…”