Non-terpenoid Alkaloids

Other metabolites derived from isoprenyltryptophan and amino-acids which have been encountered recently include roquefortine. 

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Non-terpenoid Alkaloids.—De-A-methylation of lysergic acid and derivatives can be achieved using a variant14 of the classical von Braun procedure which involves successive treatments with cyanogen bromide and zinc-acetic acid (or hydrogen-Raney nickel). 

Non-terpenoid Alkaloids.— The structure (14) adduced for austamide, a metabolite from Aspergillus ustus, is based principally on a thorough n.m.r. analysis [see data on (14)]. Like the brevianamides it is made up of proline,... 

A variety of other plant compounds are bioactive as toxins, pro-toxins, sweet or bitter tas-tants, odorants, semiochemicals, enzyme inhibitors, receptor agonists, receptor antagonists or psychoactive agents. The structure and bioactivity of non-alkaloid, non-phenolic and non-terpenoid plant compounds is briefly reviewed below. Some selected structures of cyclic compounds in this category are shown in the Appendix (Section 4). 

The biosynthesis of the isoprenoid moiety of terpenoid alkaloids has been reviewed. It has been found ° that catharanthine (which accumulates in Vinca rosea) inhibited a membrane-bound monoxygenase that oxidized geraniol at C-10. The inhibition was reversible and non-competitive in solubilized preparations of the enzyme and hence was probably not due to disruption of membranes. Other alkaloids that were produced as end-products were less inhibitory and catharanthine may mediate feed-back control of alkaloid biosynthesis in vivo. 

Non-terpenoid Quinolines.- Hapovine, a new alkaloid from Haplophyllum popovii, was shown by spectroscopic studies to be 2-(n-... 

These alkaloids can also be derived from non-aminoacid precursors. The N atom is inserted into the molecule at a relatively late stage, for example, in the case of steroidal or terpenoid skeletons. Certainly, the N atom can also be donated by an amino acid source across a transamination reaction, if there is a suitable aldehyde or ketone. Pseudoalkaloids can be acetate and phenylalanine-derived or terpenoid, as well as steroidal alkaloids. Examples of pseudoalkaloids include such compounds as coniine, capsaicin, ephedrine, solanidine, caffeine, theobromine and pinidine (Figure 6). More examples appear in Table 1. 

Biosynthesis of Polyketides Phenolic Compounds derived from Shikimate. The Biosynthesis of CB - Cjg Terpenoid Compounds Trrterpenoids Steroids, and Carotenoids Non-protein Amino-acids, Cyanogenic Glycosides, and Glucosinolates Biosynihesis of Alkaloids. 

Removal of non-basic impurities. In the work-up of a crude mixture of water-insoluble alkaloids, isolation procedures are often impeded by the presence of persistent non-basic impurities that are difficult to remove by conventional means, including column chromatography phenols and hydroxylated terpenoid constituents are particularly troublesome in this regard. In many instances, removal can be achieved by prolonged ether extraction of a dilute sulphuric acid solution of the crude bases in a continuous extraction apparatus [128]. In one case this also failed, but a counter-current method referred to later removed the impurity. 

The biosynthesis of camptothecin (102) follows that of terpenoid indole alkaloids through strictosidine (79) The lactam (101) derived from (79), and not the C-3 epimer, is the next intermediate.Several unknown steps follow, included in which is dehydrogenation of ring d [see (101)]. In this process a proton is lost from C-14. Tritium label at this site in (101) is retained by a primary isotope effect, the result of non-stereospecific deprotonation.This indicates that removal of the proton is not enzyme-controlled (c/. papaverine biosynthesis ref. 8, p. 19). 

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