Some Miscellaneous Alkaloids

The location of one as yet unidentified carbon atom results from examination of the indolic product (CCCXX VIII) which is produced together with CCCXXIX on zinc-hydrochloric acid reduction of aspidodasycarpine diacetate (CCCXIX). The NMR and IR spectra reveal 

H2C==C—-C02Me (two one-proton singlets, 6.20 and 6.63 ppm conjugated ester, 5.85 [i.). NMR-spectra further establish the presence of the sequence ArC H2C H20H, C-6,H2 appearing at 3.0 ppm and C-5,H2 at 3.85 (triplet) shifted to 4.30 ppm in the diacetate CCCXXX. Confirmation of this side chain is seen in the mass spectra of CCCXXVIII 

Structure II now becomes the logical structure for aspidodasycarpine, the zinc and acid reduction to CCCXXVIII being explained by a mechan- 

Distinction between the two as well as confirmatory evidence were obtained by extensive decoupling studies at 100 Me. These established the presence of the series X2OH—CH(X)—CH2—CHX2 (X represents a 

In contrast with the C-21 protons the C-15 proton is considerably deshielded partly due to the fact that it lies in the plane of the 19,20 

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Each section in this chapter deals with a major class of alkaloids encountered in the Sri Lankan flora. Subsections under each section are dedicated to discussions on a particular group or subgroup of alkaloids. Alkaloids that do not belong to any of the major classes are considered in the section on miscellaneous alkaloids. This approach was preferred over a discussion based on plant taxonomy used in an earlier review on this subject (8). However, Table IV presents the Sri Lankan plant species (arranged in alphabetical order) from which alkaloids have been isolated, together with the families to which these plants belong and the alkaloids encountered. Some conclusions on the current status and future prospects are drawn at the end of the chapter. 

Also included is a chapter dealing with the chemistry of the Lycopodium alkaloids and one treating a group of miscellaneous alkaloids. Many of the latter are as yet not relegated to a particular type, although on some of them considerable work has been done in the interval following the publication of the first volume, while in several the structures have been entirely or almost entirely elucidated. 

In the last group alone, there are more than 160 members, some of which are toxic. Many other alkaloids, some of great complexity, can be found in plants and frequently are referred to by the plant name. Thus, the Amaryllidaceae (exemplified by the common narcissus plant) alkaloids are a rich collection of complex stmctures. From the moss family Lycopodiaceae are obtained a group known as the Lycopodium alkaloids. Many miscellaneous alkaloids also are known. The book by Aniszewski is an excellent source of information on other types of alkaloids, their botanical distribution, and their biological and other features. 

Fig. 36.6. Some miscellaneous types of sesquiterpene alkaloids and pulchellin.

The most popular and commonly used chiral stationary phases (CSPs) are polysaccharides, cyclodextrins, macrocyclic glycopeptide antibiotics, Pirkle types, proteins, ligand exchangers, and crown ether based. The art of the chiral resolution on these CSPs has been discussed in detail in Chapters 2-8, respectively. Apart from these CSPs, the chiral resolutions of some racemic compounds have also been reported on other CSPs containing different chiral molecules and polymers. These other types of CSP are based on the use of chiral molecules such as alkaloids, amides, amines, acids, and synthetic polymers. These CSPs have proved to be very useful for the chiral resolutions due to some specific requirements. Moreover, the chiral resolution can be predicted on the CSPs obtained by the molecular imprinted techniques. The chiral resolution on these miscellaneous CSPs using liquid chromatography is discussed in this chapter. 

Each alkaloid has also been characterized by its UV-, IR-, and NMR-spectrum. This information together with some degradative work permits the recognition of the three classes of alkaloids listed in Table I (1) tetracyclic lactones, (2) highly oxygenated hexacyclic esters, and (3) one hexacyclic and two pentacyclic bases of low oxygen content. Several alkaloids, as yet unclassifiable, are collected in the inevitable miscellaneous group. 

Cassane and Miscellaneous Tricyclic Diterpenoids.—A group of furanoid diterpenoids, related to the caesalpins, has been isolated from Pterodon emargina-and P. pubescens. They include compounds (39—42). Some further diterpene alkaloids of the cassaic acid class have been isolated from Erythro-phleum ivorense. 

The following is supplementary to Volume VII, Chapter 24, page 509. This is a miscellaneous group of plants which have been shown to contain alkaloids for which some reliable properties have been recorded. The plants are listed alphabetically and, when warranted, the alkaloids are treated separately under their own headings. Where known the structures of the alkaloids are given. 

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