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

Abstract

The mass spectra of annotine and some of its derivatives are recorded and discussed. Fragmentation mechanisms are proposed to account for the formation of the major pealis in the spectra. T h e composition of the ions has been verified by measurement of the high-resolution spectra of four of the five compounds. The results lend support t o the structure previously proposed for this allraloid.In a recent publication (I) it was proposed that annotine (2-5) has structure I. This proposal was based upon a number of degradation experin~ents, upon the examination of annotine and some of its derivatives by infrared and nuclear magnetic resonance spectroscopy, and upon biogenetic considerations. In this con~lllunication we report on the mass spectrometric examination of annotine and some of its derivatives.The mass spectra of a representative group of Lycopodiunz alltaloids were reported several years ago (6); they sho\ved that the loss of the bridge carbon atoms was characteristic of all alkaloids examined. Since then mass spectrometric studies have been used as an aid in the elucidation of the structure of several ne\v allcaloids of this family, and in all cases this behavior has again been observed. Among other allcaloids, lycodoline (6,7), des-N-inethyl-hydroxy-a-obscurine (8), and lycofawcine (9), which carry a hydroxyl group a t C4 in the hydrojulolidine system, as has been proposed for annotine, \\-ere investigated. In the spectra of the first t\vo of these colnpounds a large PI-17 peak was observed as a result of loss of a hydroxyl radical. The All-17 ion so formed then under-\.\rent further fragmentation with loss of the bridge carbon atoms. Lycofawcine and its derivatives do not exhibit a prominent AfI-17 pealc, but the Cq hydroxyl is eliminated along with the bridge carbon atoms. One might expect that, if annotine has structure I, its fragmentation urould follo\\i a pattern sinlilar to that of other allcaloids bearing a C4-OEI group. This expectation was borne out, as the results reported below indicate.The major peaks in the mass spectrum of annotine, shown in Fig. l a , may be explained by involting two fragmentation processes. In one process the first step involves loss of the hydroxyl group, giving rise to an ion of mass 258. A metastable peak a t nz/e 242.0 is in accord with this change; the value of m* calculated for the transforination 275 -+ 258. is 242.0. The pealis observed a t m/e 172 and 144 may be considered to arise fro111 the ion of mass 258 as shown in Scheme la. A metastable pealc associated \\.it11 the change 258 -+ 172 is observed a t nz/e 115.0 (m* calcd. = 114.7). The last step, m/e 172 -+ 144, is analogous to the m/e 174 -+ 146 transfor~nation encountered in the fragmentatioil of dihydrolycopodine and other Lycopodiztnz allialoids (6).

Mass spectrometry

“…Fragmentation processes and/or mass spectra are presented for quinoline (i486), isoquinoline (1348), several benzylisoquinoline (1478), various bisbenzylisoquinoline (87,106,627,1346,1480), some bisbenzyltetrahydroisoquinoline (417, 1077), bisphenethylisoquinoline (HI), and imidazolylqumoline (768,949), calcanthaceous (648), codeine salts (I445), coryrantheine (932), crotonosine-related materials (91), dimeric piperidine alkaloids (1247), diterpene alkaloids (1201), and heptacyclic (110,536), lactone (457), lycopodium (1009), lycorine (761,885), morphine (1561), pentacyclic oxindole (1347), phenolic (1182), piperidine (983), proaporphine (1479), pyrazole (1326), pyrrolizidine diester (56), quaternary (708,709,713,861), rhizophoraceae (366,1586), rhoeadine (455), and 4-quinazolone (50) alkaloids.…”

An NMR study of the Lycopodium alkaloids, annotinine and annotine: verification of the annotine structure

“…The structure assigned to annotine (1,2) (Fig. l), a minor , component of the alkaloids of Lycopodium annotinium L., is I unique among the more than 100 alkaloids of established 1 structure of the Lycopodium family (3).…”