Alkaloids mass spectra

Dieckmann reaction, 4, 471 Indolizidine alkaloids mass spectra, 4, 444 Indolizidine immonium salts reactions, 4, 462 Indolizi dines basicity, 4, 461 circular dichroism, 4, 450 dipole moments, 4, 450 IR spectra, 4, 449 reactivity, 4, 461 reviews, 4, 444 stereochemistry, 4, 444 synthesis, 4, 471-476 Indolizine, 1-acetoxy-synthesis, 4, 466 Indolizine, 8-acetoxy-hydrolysis, 4, 452 synthesis, 4, 466 Indolizine, I-acetyl-2-methyI-iodination, 4, 457 Indolizine, 3-acyloxy-cyclazine synthesis from, 4, 460 Indolizine, alkyl-UV spectra, 4, 449 Indolizine, amino-instability, 4, 455 synthesis, 4, 121 tautomerism, 4, 200, 452 Indolizine, 1-amino-tautomerism, 4, 38 Indolizine, 3-amino-synthesis, 4, 461, 470... 

Hydroxyneothiobinupharidine (28) was also isolated from Nuphar lutea (37, 38). Reduction of 28 with NaBH4 and NaBD4 resulted in neothiobinupharidine (17) and neothiobinupharidine-6 -d, thus proving the skeleton of the alkaloid. Mass spectra, lH NMR, and CD measurements finally furnished the position of the hydroxyl group and the (5) configuration for C-7. ... 

In recent years mass and nmr spectral methods have been increasingly utihsed in the structure determination of Erythrina alkaloids. Mass spectra have proved particularly useful in preliminary screening of Erythrina species for their alkaloid content especially in conjunction with gas chromatography (Games et al. 1974, Hargreaves et al. 

The first 125 ml of eluent contained no alkaloids, but the next 150 ml yielded a crude alkaloid (115 mg). This alkaloid was crystallize from alcohol to yield 59 mg of slightly colored plates, mp 113-115. Subsequent recrystallizations raised the melting point to 121-122° (pale-yellow plates). The mass spectrum exhibited a parent ion at m/z 353. The UV spectrum showed maxima at 260 and 332 nm,... 

In comparing the mass spectra of ene lactams, a conclusion can be reached that they all undergo a similar major fragmentation under electron impact. The spectra show the presence of peaks of molecular ions and peaks formed by the loss of a molecule of dimethylamine from M+. The base peak at m/z 58 is present in spectra of all these alkaloids as are the peaks representing ions of type 122 arising from the upper part of the molecules. The mass spectrum of fumschleicherine (120) (120,121) is very similar to that of fumaramine (111), yet a weak peak at m/z 398 represents the molecular ion, which loses a molecule of water prior to the major fragmentation. 

During a search for physiologically active compounds in South African plants, a new hasubanan ester acetal alkaloid, methylstephavanine (6), was isolated from Stephania abyssinica (19). The H-NMR spectrum of the new alkaloid 6 exhibited signals for one methylenedioxy, one N-methyl, and four methoxyl groups (19) (Table II). Its mass spectrum revealed the most abundant ion peak at m/z 229, indicating a close resemblance to the known hasubanan alkaloid, stephavanine (18). 

Basic hydrolysis of 6 afforded alcohol 19 and methyl veratrate. The H-NMR spectrum of 19 (Table II) revealed the presence of one methylenedioxy, one N-methyl, and two methoxyl groups. The mass spectrum (Table IV) exhibited the most abundant and significant ion peak at m/z 229 indicative of metaphanine-type cleavage. Treatment of an aqueous THF solution of stephavanine (18) with excess sodium hydride and methyl iodide gave N.O-dimethylstephine, a compound identical to alcohol 19. Thus, the structure of the new alkaloid 6 was established by chemical correlation with stephavanine (79). 

A new amorphous alkaloid has been recently isolated from the Chinese plant T. bufalina (Ervatamia hainanensis) collected on Hainan Island (53). Its mass spectrum showed a molecular ion at m/z 382, corresponding to C23H30N2O3. From the fragmentation pattern, this compound would appear to be a coronaridine derivative in which a C2H50 unit is attached to the aliphatic moiety of the molecule. The structure 111 with (S) configuration at C-3 was determined by a detailed analysis of its H-NMR spectrum (Table IV) in comparison with the data of other ibogan alkaloids. 

Compound 172 exhibited typical indolenine UV absorptions and mass Spectral fragmentation very similar to those of 15,20-anhydrocapuronidine (303), obtained by concentrated H2S04 dehydration of 170. Upon reduction with NaBH4, the indolenine 172 was converted to its 1,2-dihydro derivative, identical to the natural product 173. Catalytic hydrogenation gave a tetrahydro derivative, characterized by a peak at m/z 190 in the mass spectrum, typical of pseudoaspido-spermatane alkaloids. 

The structure of the 3-oxo derivative 65 was determined by high resolution mass spectrometry, which demonstrated that a single oxygen atom had been incorporated into the alkaloid skeleton. Peaks in the mass spectrum at mte 174 and 188 provided evidence that the additional oxygen atom was not in the dihydroindole portion of the molecule, while a peak at mte 138 supported the presence of an oxygenated piperdine ring. This metabolite was also chemically compared with authentic oxodihydrovindoline derivatives previously prepared and provided for comparison by J. P. Kutney. 

Leurosine (75) (Scheme 20) is the most abundant of the dimeric antitumor alkaloids isolated from Catharanthus roseus G. Don. Several species of Strep-tomyces produced a common metabolite of the alkaloid, and S. griseus (UI1158) was incubated with 400 mg of leurosine sulfate to obtain 28 mg of pure metabolite (180). The metabolite was identified as 76 primarily on the basis of its H-NMR spectrum. The mass spectrum indicated that the metabolite contained one oxygen atom more than 75. The H-NMR spectrum contained all of the aromatic proton signals of the vindoline portion of the molecule, and aromatic proton signals for the Iboga portion of the compound occurred as a doublet of doublets... 

The mass spectrum of xylopinine 1191. a protoberberine alkaloid, shows an ion 20, having an o-quinodimethane system, together with a 3,4-dihydroisoquinolinium ion (21) (Scheme 3.6). 

In 1987, Eurukawa et al. reported the isolation of oxydimurrayafoline (195) from the root bark of M. euchrestifolia. This alkaloid represented the first example of a dimeric carbazole alkaloid with an ether linkage (69). The UV spectrum (/Imax 242, 253, 294, 324, and 337nm) and the base peak at m/z 211 in the mass spectrum of oxydimurrayafoline (195) indicated a symmetrical dimeric carbazole with two murrayafoline A units. The H-NMR spectrum resembled that of murrayafoline A (7), except for the presence of a singlet at 8 4.76 instead of the singlet for the aromatic methyl group in murrayafoline A at 5 2.42. The singlet at 8 4.76 suggested a benzylic oxymethylene moiety. The spectral data, supported by NOE experiments, led to structure 195 for oxydimurrayafoline (Scheme 2.46). 

Dioxo-3-isoparteine was isolated from Lupinus sericeus (143). The mass spectrum, with M+ at miz 262 and signals at miz 234 (M" — 28) and 206 (M+ - 56), is characteristic for 10- and 17-oxosparteines and successive splitting of two carbonyl groups. Oxidation of p-isosparteine (14) by potassium ferricyanide resulted in 10-oxosparteine (108) as well as 10,17-dioxo-p-isospar-teine (109) (Scheme 13). This confirmed the alkaloid structure. Although 109 was found as a natural compound it had already been synthesized by Bohlmann et al. (144). The problems of configuration and conformation of sparteine (6), a-isosparteine (7), and (3-isosparteine (14) were discussed (145). 

Epiaphylline was isolated ftomLupinus hartwegii (146-147). The mass spectrum of this alkaloid is characterized by peaks at m/z 248 (70), 247 (46), 220 (45), 137 (47), 136 (100), 97 (53), and 96 (45%) that are tyical for sparteine alkaloids. The peak at m/z 220 originates from the splitting of a carbonyl group. Epiaphylline (110), in contrast to aphylline (108), did not react under mild catalytic hydrogenation conditions, but under harsher conditions epiaphylline (110) converted to 3-isosparteine (14) (Scheme 14). This established the presence of a carbonyl group at C-10. 

The mass spectrum of leontidine is characterized by intensive ion peaks at miz b0 and 4b typical for qu inoYizidine alkaloids. Ion peaks at m/z % and 84 speak for the tjiesence of a five-membeted heterocyclic ring,. 

Albertidine, isolated from Leontice Albertii Rgl. (196,197), is a crystalline, optically active tribase. There are IR absorption bands for a trani-quinolizidine system at 2750 and 2793 cm and a six-membered lactam carbonyl at 1640 cm The absorption in the fingerprint region is similar to that of matrine. The mass spectrum of albertidine is characterized by ion peaks at miz 247 (M -1), 219, 205, 192, 177, 150, 137, 98, and 96 which are typical for matrine alkaloids (209). On the basis of spectroscopic data and taking into account the tranj-quinolizidine band in the IR spectrum, the probable structure 182, with rings A/B-trans, was proposed. 

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