Structure of the Alkaloids

Isolation of seven alkaloids from the Calabar bean is reported to date (Fig. 1). Of these, the structures of (-)-calabatine (6) (C17H25N2O3) 

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Amongst products isolated from Heliotropium spathulatum (Boraginaceae) were 9 mg of a new alkaloid which gave a positive Ehrlich reaction with p-dimethylaminobenzaldehyde The molecular formula determined by mass spectrometry is CisH2sNOs. What is the structure of the alkaloid given the set of NMR results 54 Reference is useful in providing the solution to this problem. Conditions CDCI3, 9 mg per 0.3 ml, 25 °C, 400 MHz ( //), 100 MHz ( C). (a) HH COSY plot ... 

Dihydroflavopereirine (3) has been isolated from Strychnos usambarenis Gilg (12). The zwitterionic structure of the alkaloid has been proved by spectroscopic investigation and by direct comparison of the alkaloid with a synthetic 5,6-dihydroflavopereirine (3) sample. 

The X-ray diffraction studies have not only helped in elucidating the complete structure of a compound in its crystalline state but also in establishing its configuration. The noteworthy feature of the method is that no recourse is taken to chemical work. Thus the structure of the alkaloid the-lepogine, C20 H31NO has been settled without chemical work. For the last two decades the method has been widely employed because it takes less time due to the use of automatic diffractometers and electronic computers. 

Process automatically the structure of the alkaloid porantherine, first with the "default-order" of disconnections and then giving priority to "consonant" over "rings" disconnections. In the latter case you should "Save" only the intermediate precursors leading to the same synthetic sequence and the same starting material (A) used in Corey s synthesis, which was actually found by LHASA (see ref. 19, Chapter 12). 

Desoxocamoensidine was isolated from Maackia amurensis Rupr. and Maxim. (187). The structure of the alkaloid (164) was established by its identity with the product obtained from camoensidine (159) with LAH (Scheme 28). 

Doepke and co-workers have isolated more new alkaloids from Hymenocallis arenicola. Havanine (1) is a new member of the crinine group the presence of two methoxyl groups and one attached to an sp3 carbon was indicated by the n.m.r. spectrum, and the structure of the alkaloid was proposed mainly on the basis of the mass spectrum.2 Structure (2) for caribine was assigned as a... 

Evidence in favor of structures 1-15 for the alkaloids in this group has been furnished in Volume XI, Chapter 10, Section II. The uncertainty relating to the structure of the alkaloids nerispine, parkamine, niflexine, and amaryllidine, however, still remains. The structures of narcissidine (Volume XI, p. 331) and of the related alkaloids parkacine (p. 332) and ungiminorine (p. 333) have, on the other hand, been revised by means of X-ray analysis. Work has been devoted to the study of the physical properties of the alkaloids in this group in an attempt to establish a general relationship between structure and behavior as well as to the study of the correlation of same with other classes of alkaloids and to the investigation of the chemical reactivity of representative members. 

The structural elucidation of mucronine-A-aldehyde (85) (39) (Scheme V) relies upon the peaks at m/e 510 (0.2%), m/e 206 (100%), and m/e 361 (11%). The first named is the molecular ion and reveals the former cyclic structure of the alkaloid. a-Fragmentation at the tertiary amine forms the fragments b and c which indicate a nuclear substituted A,A-dimethylphenylalanine unit in mucronine-A aldehyde. 

The structure of the alkaloid propyleine (C13H21N amorphous levorotatory) (156) from this beetle was determined by spectral methods supplemented by chemical methods. It is the dehydro derivative of coccinellin (143) into which it was converted (144). 

The crystal structures of the alkaloids containing a hydroxyl group at C-2 have not been determined. The stereochemistry of erythratine (42) was established as 2R,3R,5S by Barton et al. (79) and that of erythratidine (39) as 2S,3R,5S by the same group (27) on the basis of optical rotation and NMR data for both pairs of C-2 epimers (see Section II,C,4b). The configuration at C-2 for erysosalvine (45), erysotine (48), and erysopitine (50) has not been defined. 

The benzylisoquinoline alkaloids are widely distributed in nature and are intermediates in the biosynthesis of alkaloids of this family (2, 3). It is not surprising therefore that several groups (6, 7, 15, 23) have examined their spectra. Among the alkaloids that have been studied are reticuline (26) (7), norlaudanosine (27) (7), laudanosine (28) (6, 15), and the cis- and trans-N-oxides of laudanosine, 29 and 30, respectively (7). The chemical shifts of laudanosine are recorded in Table IV and the structures of the alkaloids may be found in Fig. 4. 

Non-hemiterpenoid Quinolines.—New sources of the simple quinolines 4-methoxy-l-methyl-2-quinolone and its 8-methoxy-derivative (folimine) have been reported the former was isolated from Myrtopsis sellingii9 and from Zanthoxylum cuspidatum,16 and folimine was shown to be a constituent of Haplophyllum perforatum.5 The latter species also contains foliosidine (9), previously isolated from H. foliosum. The micro-organism Pseudomonas aertiginosa has been shown to contain 2-(hept-l-enyl)-4-quinolone (12).10 The structure of the alkaloid was established by n.m.r. and mass spectroscopy and by its synthesis from aniline and the j3-keto-ester Me(CH2)4CH=CHC0CH2C02Me. 

The principal evidence for the aliphatic structure of the alkaloids was presented in Section III, B, where it was shown that they have the car-... 

Among the many alkaloids of Rhazya stricta (see Table I), the structure of the alkaloid rhazinine remains to be determined (197). This indolic base, C19H24N2O, contains a primary alcoholic group but, unlike akuammidine (CCCXXII) which accompanies it in the plant, it contains no G-methyl (197). Other alkaloids of the same plant include rhazidine, C20H26N2O3, H20, mp 278-279°, [[Pg.505]

The tropanol fragmentation pattern was very useful in establishing the structure of the alkaloid phyllalbine.62... 

The knowledge of the key fragmentation routes of eburnamine and some related alkaloids confirmed or elucidated the structures of the alkaloids 11-methoxy-vincamine,100 vincaminine,102 and vinci-nine,102 of the same skeletal type as eburnamine. Alkaloids of the mavacurine-pleiocarpamine group (212)103 are characterized by a key fragment corresponding to the loss of the ester group and... 

In addition to the study of the bis-benzo[c]phenanthridines just discussed above, Marek and coworkers have also extensively studied other benzojcjphenanthridine alkaloids [111,121]. The structures of the alkaloids for which data have been reported and their respective chemical shifts are collected in Figure 14.12. These alkaloids include the methyl chloride salts, sanguinarine chloride (110), chelrythine chloride (111), sanguilutine chloride (112) and chelirubine chloride (113). 6-Substituted and... 

The structures of other alkaloids of the pseudophrynamine class (3a-prenylpyrrolo[2,3-6]indoles) were deduced from mass spectral analysis (86). The pseudophrynamines are tabulated below. In addition to the listed pseudophrynamines, other trace analogs of pseudophrynamine A (XV) with molecular ions at miz 526,540, and 542 were detected. The structures of the alkaloids of the pseudophrynamine class from frogs of the genus Pseudophryne are shown in Fig. 22. 

An intramolecular nucleophilic epoxide cleavage of this type was used to convert 1 into 2, an intermediate in a synthesis of 3, which was originally believed to be the structure of the alkaloid cannivonine of the New Brunswick cranberry. ... 

The structure of the alkaloid triacanthine, isolated from Gleditsia triacanthos L. in the early fifties, was unknown for almost 10 years. The alkaloid was synthesized in 1961 and its structure confirmed unambiguously as 3-(3-methylbut-2-enyl)-3f/-adenine (17). ... 

Fig. (14). Proposed structures of the alkaloid 275A [16] 4,6-Disubstituted Quinolizidines...

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