Calabar alkaloids

Cacalia hastata, 601 Cacotheline, 566 Cactaceae, 154 Cadaverine, 518 Calabar bean alkaloids, 539 Calabarine, 540 Calabash curare, 373 alkaloids, 380... 

The alkaloid physostigmine found in the calabar bean is another classic milestone molecule in total synthesis. Metrics for thirteen plans to this molecule are summarized in Table 4.25. 

Matsuura, T, Overman, L.E., Poon, D.J. (1998) Catalytic Asymmetric Synthesis of Either Enantiomer of the Calabar Alkaloids Physostigmine and Physovenine. Journal of the American Chemical Society, 120, 6500-6503. 

Node and Fuji have developed a new chiral synthesis of various alkaloids using chiral nitroalkene, (S)-(-)-2-methyl-2-(2 -nitrovinyl)-S-valerolactone. Scheme 8.11 shows a total synthesis of (-)-physostigmine, a principal alkaloid of the Calabar bean.53 The key nitroalkene is prepared by asymmetric nitroolefination of a-methyl-8-lactone using a chiral enamine (see... 

The classic cholinesterase inhibitor is the alkaloid physostigmine (6)/ eserine (7). It was first isolated from the calabar bean, the seeds of Physostigma venenosum. Many novel natural products with AchE-inhibifing properties have shown promise as therapeutics for AD. Some examples of such products (pure compounds/plant extracts or formulations) are briefly reviewed here. 

The classic cholinesterase inhibitor is the alkaloid physostigmine (33), also called eserine. Investigations carried out in the nineteenth century on the ordeal poison esere, which consisted of an extract of the Calabar Bean, the seeds of Physostigma venenosum Balf, resulted in the isolation of (33)... 

It is a tertiary ammonium alkaloid obtained from the Calabar bean, the dried ripe seed of Physostigma venenosum, which... 

Takano S and Ogasawara K (1989) Alkaloids of the calabar bean. The Alkaloids, Chemistry and Pharmacology (ed Brossi A) Vol 36. Academic, San Diego, pp 225-251. 

In the mid-19th century the Calabar bean was sent to Scotland and the two principal alkaloids were extracted in a number of European laboratories. There the formulae were determined and toxic and medicinal properties intensively studied. By the early 20th century the formula for physostigmine and the presence of two... 

Physostigmine is one of the major alkaloids in calabar bean. It has been shown to inhibit acetylcholinesterase at low concentration and to reverse the toxic effects resulting from diazepam overdose. The phytostigmine skeleton is easily obtained in very good yields from an appropriate non-stabilized imidate methylide.162,292,465... 

Upon Julian s return to the United States, DePauw University offered him a faculty position and research support. His first project was the total synthesis of physostigmine, an indole alkaloid extracted from the Calabar bean, used in the treatment of glaucoma. Sir Robert Robinson at Oxford University in England was also working on this synthesis. Julian achieved the synthesis of physostigmine, and showed that Robinson s hypotheses about its structure were wrong. 

Another fruitful means of identifying pharmacologically active natural products has been that of folk law remedies, many of which are plant products. Typical examples include alkaloids, such as atropine (from plants of the Solanaceae family, known to the ancient Greeks) and reserpine (from Rauwolfia serpentina, the snakeroot), which is popular in India as a herbal remedy for use as a tranquilizer or antihypertensive. Other chapters in the book relate to stigmines (based on phy-sostigmine, an anticholinesterase alkaloid from the Calabar bean in West Africa) that are used to treat Alzheimer s disease (Chapter 11-12), and opioid receptor ligands (based on morphine, the most important alkaloid of the opium poppy) for pain relief and as antitussives (Chapter 11-11). 

The chemistry of the alkaloids of the Calabar bean up to the year 1952 has been discussed fully in Chapter 13 (Section XI) of Volume II of this series. More recent work (up to 1960) has been described briefly in Chapter 10 of Volume VII of this series. The present chapter, then, will only briefly outline investigations reported prior to 1952, but will deal more extensively with work reported since that time. 

The alkaloids are obtained from the seeds of the Calabar bean (Physo-stigma venenosum Balf.), which is a tropical woody vine. The beans were used for many years as an ordeal poison in West Africa. 

The alkaloids isolated from the Calabar bean are listed in Table I. The principal alkaloid found in the beans is physostigmine. 

The Physical Constants of the Alkaloids Isolated from the Calabar Bean... 

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