The isolation and characterization of 19
new alkaloids from the bark of Galbulimima species is described. After some
corrections to previous work, the number of alkaloids from this source now
stands at 28.
By an extensive series of degradations
involving dehydrogenation, exhaustive methylation, and oxidation, the structure
of himbacine is established. It is the first member of a new group of
alkaloids. By simple transformations, himbeline, himandravine, and himgravine
are shown to be closely related to himbacine and their structures also
established.
A study of the reactions of o- methoxyphenyltrimethylstannane and o- methoxyphenyltributylstannane with lead tetraacetate has been carried out. This has led to the development of a new high-yielding
route to aryllead triacetates, which involves the treatment of an aryltributylstannane with lead tetraacetate and a catalytic amount of a mercury(II) compound in chloroform. The reaction has been shown to be quite general, giving good results with electron-rich and electron-deficient aromatics.
Aryl-, vinyl-and alk-1-ynyl-lead(w) tricarboxylates act as electrophilic arylating, vinylating and alkynylating agents, respectively, with a variety of nucleophiles, especially soft carbon nucleophiles such as B-dicarbonyl compounds, phenols and nitroalkanes. In their reactions, they show a marked preference for carbon-carbon bond formation, especially in which a quaternary centre is produced. The formation and the synthetically useful reactions of these new reagents are reviewed.
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