Biogenetic precursors

Epinephrine itself does find some use in clinical medicine. The drug is used in order to increase blood pressure in cases of circulatory collapse, and to relax the bronchial muscle in acute asthma and in anaphylactic reactions. These activities follow directly from the agent s physiologic role. The biogenetic precursor of epinephrine, norepinephrine, has activity in its own right as a mediator of sympathetic nerve action. (An apocryphal story has it that the term nor is derived from a label seen on a bottle of a key primary amine in a laboratory in Germany N ohne... 

Secoquettamine (234) and dihydrosecoquettamine (235) together with their probable biogenetic precursor quettamine (236) form a small group of alkaloids. They were isolated by Shamma et at. (179) from Berberis baluchista-nica in yields of 0.00036,0.00017, and 0.0012%, respectively. These alkaloids incorporate either a benzofuran or a dihydrobenzofuran ring within the molecular framework, and the seco ones possess the /V,W-dimethylaminoethyl substituent. The structures of these bases were determined on the grounds of spectral data as well as by total synthesis. There is one chiral center at C in dihydrosecoquettamine (235) however, the base was isolated in the form of a racemic mixture (179). 

Didehydrogeissoschizine (147) has been proposed to be the biogenetic precursor of simple indolo[2,3-a]quinolizine alkaloids such as flavopereirine (148)... 

It is interesting to note that while vindoline and catharanthine are abundant in Catharan-thus roseus (L.) G. Don, a carbomethoxycleavamine (the initially presumed biogenetic precursor of the binary alkaloids), could not be detected or isolated. This suggested to Atta-ur-Rahman (45) that the VLB-type alkaloids are formed by union of Iboga and Aspidosperma alkaloids, an idea reinforced by biochemical studies (46-49). 

It is interesting to note that these experiments strongly suggested that anhydrovinblastine is the biogenetic precursor of the VLB-type alkaloids in the plant, a proposal recently substantiated (47,48,82-88). 

Pyoverdin-like siderophores with other chromophores have also been observed (see Fig. 1) (45). The 5,6-dihydropyoverdins (Chra without the 5,6-double bond) and the ferribactins (Chrc) are considered to be biogenetic precursors of the pyoverdins 318) (the term ferribactin was originally used for the Fe " complex 221) and later for the free ligand). An azotobactin chromophore (Chrd, see also below Sect. 2.2) is occasionally found in Pseudomonas isolates e.g. 146)). Siderophores produced by a specific Pseudomonas strain but differing in the chromophore always have identical peptide chains. 

Aromatic amino acids are biogenetic precursors of neuroamines (dopamine, serotonin, histamine, etc.). On the other hand, phenylalanine (Phe) is frequently present in peptide sequences, while tyrosine is an important site of phosphorylation of proteins. Aromatic amino acids and neuroamines fluorinated on the aromatic ring have been the focus of many investigations. Indeed, after incorporation in polypeptides and proteins, they can be used as probes in NMR and in PET. 

Loganin is the biogenetic precursor of secologanin, which is a key intermediate in the biosynthesis of a ... 

A number of monocyclic and benzo-annelated examples of 1,2- and 1,3-thiazepines have been prepared but there has been little systematic study of these systems. The interesting photochemical interconversions of pyridine N-imides into 1,2- and 1,3-diazepines and of pyridine Af-oxides into 1,2- and 1,3-oxazepines regrettably lack parallels in thiazepine chemistry. There has been more interest in 1,4-thiazepines, as both rearrangement products and possible biogenetic precursors for penicillins and because of the pharmacological value of the benzo- and dibenzo-[l,4]thiazepines as antidepressants and coronary vasodilators. The only review (70ZC361) is excellent but not very recent. 

The halogenated acyclic marine monoterpenes are often considered to be the biogenetic precursors of the alicyclic monoterpenes that are presented in this section. Many of the preceding algae species also contain cyclic monoterpenes. As was the case in preceding sections only newly characterized compounds are numbered and the reader is referred to the first survey for structures of previously isolated compounds (7). 

Laurencia obtusa from the western coast of Ireland has afforded scanlone-nyne (689), the first reported study of Laurencia red algae from Irish waters (786). A Japanese Laurencia sp. contains the new bisezakyne-A (690) and -B (691) (787). The red alga Ptilonia magellanica is the source of pyranosylma-gellanicus A-C (692—694) and the linear 695, a possible biogenetic precursor (788). 

Cueto M, Darias J, Rovirosa J, San-Martin A (1998) Pantoneurotriols Possible Biogenetic Precursors of Oxygenated Monoterpenes from Antarctic Pantoneura plocamioides. Tetrahedron 54 3575... 

Lindel T, Hochgiirtel M, Assmann M, Kock M (2000) Synthesis of the Marine Natural Product Wa-(4-Bromopyrrolyl-2-carbonyl)-L-homoarginine, a Putative Biogenetic Precursor of the Pyrrole-Imidazole Alkaloids. J Nat Prod 63 1566... 

From a Japanese sponge of the genus Haliclona two cytotoxic alkaloids, haliclamines A and B (252 and 253), were isolated (213). They are proposed to be biogenetic precursors of the petrosins or sarains. 

Lindheimerine occurs in extremely small quantity by comparison with ovatine. Since these two alkaloids are closely related chemically, we suggest that lindheimerine may be a biogenetic precursor of ovatine. These alkaloids did not exhibit any antitumor activity in vivo or in vitro. 

The authors were unable to carry out any transformation of staphinine and staphimine to staphisine and staphidine, respectively, because of the instability of these alkaloids toward various mild reducing agents (e.g., sodium borohydride, sodium cyanoborohydride). Staphimine and staphinine occur in extremely small amounts in the seeds of D. staphisagria. It has been suggested that the imine-containing alkaloids may be biogenetic precursors of staphisine and staphidine. 

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