Karrer - Molecules

Since its discovery in 1909, the elucidation of its structure by Karrer in 1931 [5] and its first total synthesis [6], vitamin A has represented a challenging target molecule for chemists [7], The first industrial synthesis of retinol was performed at Hoffmann-La Roche (H-L R) [8], followed by other approaches of the Baadische Anilin- Soda Fabrik (BASF AG) [9], and Rhone-Poulenc (R-P) (today Aventis) [10]... 

Wulf, and Karrer attempted to repeat some of the previous work in the presence of ozone, which ensures the complete absence of lower oxides since it oxidizes them instantaneously to the pentoxide. In the decomposition of the pentoxide, therefore, there should be a period of induction during which the decomposition products are re-oxidized by the ozone. When all the ozone is used up brown fumes should appear and the decomposition of the pentoxide should go forward in the normal way. It appeared, however, that when the lower oxides were removed in this way the decomposition did not take place at all. This led to the conclusion that the reaction was not, after all, a simple unimolecular decomposition but a change depending on collisions between molecules of nitrogen pentoxide and molecules of nitrogen dioxide. 

An alkaloid had been isolated from this plant in 1936 (44), but Karrer and Eugster (45) succeeded in obtaining it in a pure state. Palustrine, CnH2902K3 (m.p. 121°, [a]i -fl5.8°), forms a number of crystalhne salts with indefinite melting points. Methoxyl is absent but one double bond and two active hydrogens are present in the molecule. In mice subcutaneous injections of the alkaloid cause a primary excitation rapidly fol-... 

C uv, ( 455,520 nm. /S-C. is the most abundant carotene in the animal and plant kingdoms. It was first isolated by Wackenroder in 1826 from carrots (Dau-cus carota, Apiaceae). Willstatter determined the molecular formula in 1907 and Karrer the constitutional formula in the early 1930 s. fi-C. is the provitamin A, which is oxidatively cleaved in animals to yield 2 molecules of retinal and subsequently reduced to retinol (vitamin A) (see pigments of vision). 

C24H20O10, Mr 468.42, needles, mp. 220-225 °C (decomp.) soluble in acetone. A tridepside which, on hydrolysis with concentrated sulfuric acid, gives 3 molecules of orsellinic acid. It occurs in numerous lichens, especially species from the families Umbilicariaceae, Parmeliaceae, and Roccellaceae. iU/. Aust. J.Chem.48,1761 (1995)" Culberson, p. 119-120 Karrer, No. 1048 Phytochemistry 42, 839 (1996). -[CAS548-89-0]... 

Biogenesis of the Carotenoids.— According to Karrer, the alcohol phytol, CgoHgg.OH, which forms about one-third of the chlorophyll molecule, is the parent substance of the carotinoids. Condensation of two phytol residues would in theory yield lycopene, from which the other carotinoids could arise by closure of the terminal groups to form rings. The symmetry of the carotinoid molecule suggests an origin from such a precursor. 

Karrer, Paul (1889-1971) Swiss organic chemist. Karrer was famous for his work on vitamins and vegetable pigments. In 1930 he determined the structure of carotene. In 1931 he synthesized vitamin A, having worked out the structure. Karrer was aware of the similarity between the two molecules. He subsequently determined the structures of each and synthesized riboflavin (vitamin B2) in 1937 and tocopherol (vitamin E) in 1938. Karrer shared the 1937 Nobel Prize for chemistry with Norman HAWORTH for the constitution of carotenoids, flavins, and vitamins A and B . Karrer wrote an influential textbook entitled Textbook of Organic Chemistry (1927). 

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