An Investigation of the Mills-Nixon Effect in Pyridines

“…We may be certain, therefore, of the presence of a 2,3-disubstituted pyridine ring in lycodine. Recently Godar and Mariella (14) have recorded the ultraviolet absorptioil spectra of 2,3-lutidine, 2,3-trimethylene-, 2,3-tetramethylene-, and 2,3-pentamethylenepyridine both as free bases and as salts. Their data have been replotted in Fig.…”

mentioning

confidence: 99%

Lycodine, a New Alkaloid of Lycopodium Annotinum

Anet¹,

Eves²

1958

Can. J. Chem.

View full text Add to dashboard Cite

LYCODINE, A NEW ALKALOID O F LYCOPODIUM ANNOTINUM1r \ new allcaloid, lycocline, CliHYINd, m.p. llSO, has been isolated fro111 Lycopodizr?rt a n -?~o t i n z~n l .Lycodine is a tetracyclic diaciclic base containi~lg a secontlary nitrogen atom, a 2,3-disubstit~ited pyridine ring, and a C-methyl group. T h e 2,3-dis~ibstit~1tion is in the form of a saturatecl sis-niemberecl ring.The all;aloids of Lycopodiu7n nnnokinz~m L. have been sti~died by several groups of worlters in Canada and in Europe (1, 2, 3, 4, 5 ) . The structure of annotinine, C1SH2103N, which is the main alkaloid of this species, is now known (6, 7) and is of a quite novel type. I t therefore becomes of interest to study the chemical structure of the minor alkaloids of this plant.During the process of developing suitable methods for the separation of the many minor alkaloids which have been reported to occur in this Lycopodium species, we noticed that certain fractions possessed ultraviolet absorption characteristic of a pyridine chromophore, inore or less submerged behind general absorption. This paper describes the isolation, characterization, and partial cletermination of the structure of a new alkaloid, lycodine, which was responsible for this characteristic Absorption.Lycodine was concentrated by countercurrent distribution of the allcaloid mother liquors from the crystallization of annotinine. Two successive countercurrent distributions were carried out, first in six large separatory funnels \vith the system chloroform-buffer of pH 6 and then in a 60-tube Craig machine with the system chloroforn~-buffer of pH 5.2.From these countercurrent distributions an all;aloid fraction was obtained which hacl the correct ultraviolet absorption. By chron~atography of this fraction on activatecl alumina pure crystalline lycodine was obtained.Lycodine, m.p. l l S O , [a],, -lo0, had the fornlula C17H2.LN? and gave a characteristic dipicrate, m.p. 229'-233' (decomp.), which was sparingly soluble in methanol. Titration of the base in 50% methanol showed that the pK,'s of the base were 3.97 and 8.08. One C-methyl group was found to be present by the Kuhn-Roth method. The ultraviolet spectra of the base in neutral and in acid solutions are shown in Fig. I , and correspond to an unconjugated pyridine chromophore in the base and salt forms respectively. A fuller discussion of these spectra will be left till after consideration of other results (see below).The infrared spectrum of the base (in Nujol) is shown in Fig. 2 ; the sharp band a t 3270 cm.-I must be due to a N-H group (8). As often happens (8) this band is of very low intensity in the spectrum (Fig. 2) of the carbon tetrachloride solution of the compound. The presence of a pyridine ring is confirmed by the band (9) a t 1580 cm.-I (in Nujol) and that of a C-methyl group by a band (10) a t 1382 cm.-I (in CC14). Acetylation of lycodine with acetic anhydride gave a N-acetyl clerivative, isolated as the monopicrate. Titration of the picrate showed that the acetylated base hacl only one basic center (pK, 4.95). H...

show abstract

“…The possible existence of a Mills-Nixon Effect for pyridine was first considered by Godar and Mariella in 1957. 32 They examined the UV and IR spectra of pyridines 40b, 40c and 40d ( Fig. 18a) but did not find any features which they could attribute to double bond alternation in the aromatic ring.…”

Section: Other Aromatic Nucleimentioning

confidence: 98%

“…proceeds on a preparative scale in 77% isolated yield." On the other hand, similar pyrolysis of trischloromethylmesitylene (33) affords only hexaradialene (32) and none of tricyclobutabenzene (25) (Fig. 14 We know, however, that the technique of flash vacuum pyrolysis (FVP) can often afford the efficient preparation of molecules at temperatures where they would normaIly be thermaIly unstable.…”

Section: %mentioning

confidence: 99%

The Effect of Ring Strain on Ortho‐Annelated Aromatic Molecules

Thummel

1982

Israel Journal of Chemistry

View full text Add to dashboard Cite

This paper examines the effect of fusing a small carbocyclic ring onto the ortho positions of an aromatic nucleus. Benzene derivatives are considered to which have been fused one, two or three small rings. The effect of varying the size and orientation of the rings is discussed with respect to changes in the σ‐ and π‐bonding networks, the geometry of these molecules and their chemical reactivity. Other aromatic nuclei, such as pyridine, thiophene, naphthalene and the tropylium ion, are also described. Variations in physical properties appear to be best explained by a rehybridization theory which functions in the plane of the system. Perturbations of the π‐bonding framework are better manifested by changes in chemical reactivity.

show abstract

An Investigation of the Mills-Nixon Effect in Pyridines

Cited by 24 publications

References 6 publications

Ultraviolet Spectra of Alkaloids

Ultraviolet Spectra of Alkaloids

Lycodine, a New Alkaloid of Lycopodium Annotinum

The Effect of Ring Strain on Ortho‐Annelated Aromatic Molecules

Contact Info

Product

Resources

About