Genera Considerations

Some Genera/ Considerations on B,2 Coenzymes and Model Compounds 637... 

Genera Considerations Regarding the Preparation of Singie Stereoisomers of Chiral Drugs 157... 

Most of these barks also contain considerable quantities of unnamed and uncharacterised amorphous alkaloids. The barks fall into three groups as sources of (a) alstonine, only found in A. constricta (b) villalstonine, found in Nos. (2) to (4) and (c) echitamine, isolated from Nos. (5) to (11). It is unusual to find species belonging to the same genus divided into such well-marked groups, in respect of their alkaloidal constituents. 

It grew out of another discovery in the senior author s laboratory, namely, that Reichstein s compound S could be converted in high yield into 11-epicortisol (1) by the enzymes of fungi of the genus Aspergillus The conversion of this inactive substance into the hormone cortisol thus became a problem of considerable importance. A route involving the 9,11-dehydro steroid (3) readily prepared from 11-epicortisol via its 21-acetate 11-tosylate... 

The 2D chromatograms reveal additional components of the natural mixtures. They also give a map of the essential oil, which is helpful in the identification of the components by the position and the characteristic colours of the derivatives on the plate. A further, considerable improvement in the separation performance can be obtained by using overpressured layer chromatography (OPLC). Harmala et al. (70) used 2D OPLC for the separation of coumarins from the genus Angelica. Figure 10.15 shows the one-dimensional (a) and two-dimensional (b) OPLC separations of 16 coumarins. 

The genus Fuchsia consists of perhaps 100 species, enjoys a wide distribntion, and offers a variety of systematic and evolutionary challenges. In addition to attracting purely botanical interest. Fuchsia is also of considerable horticnltnral value. Our interest in the genns concerns sect. Skinnera which consists of three New Zealand species, F. excorticata L. f., F. perscandens Cockayne Allan, and F. procumbens R. Cnnn., and the Tahitian endemic F. cyrtandroides Moore. A fourth taxon, F. x colensoi Hook. f. occurs wherever the ranges of F. excorticata and F. perscandens overlap. 

Laurencia, which has also attracted a lot of attention because of its chemical constituents, is a comparatively large genus. In addition to examples of geographically distinct chemotypes, the examples below illustrate the considerable structural variety... 

Organisms assigned to the genus Cycloclasticus have been isolated from a number of geographical locations and display a considerable metabolic versatility as follows ... 

The batrachotoxins were the first class of unique alkaloids to be characterized from skin extracts of frogs of the family Dendrobatidae (see ref. 23 for a review of amphibian alkaloids). Batrachotoxin was detected in only five species of dendrobatid frogs and these frogs were then classified as the monophyletic genus Phyllobates, based in part on the presence of batrachotoxins (24). However, levels of batrachotoxins differ considerably, with the Colombian Phyllobates terribilis containing nearly 1 mg of batrachotoxins per frog, while the somewhat smaller Phyllobates bicolor and Phyllobates aurotaenia, also from the rain forests of the Pacific versant in Colombia, contain 10-fold lower skin levels (8). The two... 

Since the discovery of tetraponerine-8 in 1987 by Braekman et al. [195] the tetraponerines, the defensive alkaloids of ants of the genus Tetraponera, have been the target of considerable synthetic efforts and have served to demonstrate the utility of various synthetic methodologies [114]. Recently a few further syntheses of these unusual tricyclic alkaloids have been reported. 

After analyzing some specimens from a pitch lake of Trinidad, Hatchett concluded that a considerable part of the aggregate mass at Trinidad was not pure mineral pitch or asphaltum, but rather a porous stone of the argillaceous genus, much impregnated with bitumen. The specimens he analyzed, however, were not representative of the lake as a whole (20). 

Two species of the genus Broussonetia, B. kazinoki and B. papyrifera, have been of considerable interest for their ethnomedical uses for the treatment of various human diseases. There is a substantial literature on the utilization of B. papyrifera, in particular, in the paper industry in East Asia. Extracts of Broussonetia species have exhibited various biological activities including antifungal, antiinflammatory, antioxidant, and antispasmodic activities. 

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