Karrer

Paul Karrer chemistry research iato constitution of carotenoids, flavins, and vitamins A and B2... 

In 1933, R. Kuhn and his co-workers first isolated riboflavin from eggs in a pure, crystalline state (1), named it ovoflavin, and deterrnined its function as a vitamin (2). At the same time, impure crystalline preparations of riboflavin were isolated from whey and named lyochrome and, later, lactoflavin. Soon thereafter, P. Karrer and his co-workers isolated riboflavin from a wide variety of animal organs and vegetable sources and named it hepatoflavin (3). Ovoflavin from egg, lactoflavin from milk, and hepatoflavin from Hver were aU. subsequently identified as riboflavin. The discovery of the yeUow en2yme by Warburg and Christian in 1932 and their description of lumiflavin (4), a photochemical degradation product of riboflavin, were of great use for the elucidation of the chemical stmcture of riboflavin by Kuhn and his co-workers (5). The stmcture was confirmed in 1935 by the synthesis by Karrer and his co-workers (6), and Kuhn and his co-workers (7). 

Photochemical decomposition of riboflavin in neutral or acid solution gives lumichrome (3), 7,8-dimethyl all oxazine, which was synthesized and characterized by Karrer and his co-workers in 1934 (11). In alkaline solution, the irradiation product is lumiflavin (4), 7,8,10-trimethyhsoalloxazine its uv—vis absorption spectmm resembles that of riboflavin. It was prepared and characterized in 1933 (5). Another photodecomposition product of riboflavin is 7,8-dimethy1-10-foTmylmethy1isoa11oxazine (12). 

M. Viscontini, C. Ebnother, and P. Karrer, Help. Chim. Acta 35, 457 (1952) M. Viscontini and co-workers. Help. Chem. Acta 38, 15 (1955). 

The stmcture of vitamin A [11103-57-4] and some of the important derivatives are shown in Figure 1. The parent stmcture is aH-Zra/ j -retinol [68-26-8] and its lUPAC name is (all-E)-3,7-dimethyl-9-(2,6,6-trimethyl-l-cyclohexen-l-yl)-2,4,6,8-nonatetraen-l-ol (1). The numbering system for vitamin A derivatives parallels the system used for the carotenoids. In older Hterature, vitamin A compounds are named as derivatives of trimethyl cyclohexene and the side chain is named as a substituent. For retinoic acid derivatives, the carboxyl group is denoted as C-1 and the trimethyl cyclohexane ring as a substituent on C-9. The stmctures of vitamin A and -carotene were elucidated by Karrer in 1930 and several derivatives of the vitamin were prepared by this group (5,6). In 1935, Wald isolated a substance found in the visual pigments of the eye and was able to show that this material was identical with Karrer s retinaldehyde [116-31-4] (5) (7). 

Vitamin is iasoluble ia water and is soluble ia 70% alcohol, cbloroform, petroleum ether, ben2ene, and hexane. Vitamin is stable ia air but should be protected from light. Although unstable ia alkaU, the vitamin is stable ia acidic medium. Its facile decomposition ia basic solution forms the basis of the Dam-Karrer color test. 

CfiHfi). Viscous yellow oil which is distd at high vacuum. It has Xmax 294nm (EJ 71). It is oxygen and light sensitive and is best stored as its stable acetate which is purified by evaporative distn at b 180-200°(bath temp)/0.7mm, [a]p +3.3° (c 5.1, EtOH). [NMR Cohen et al. Helv Chim Acta 64 1158 7987 Burton and Ingold Acc Chem Res 19 194 7986 Karrer et al. Helv Chim Acta 21 520 7988.]... 

Confirmation of Karrer s formula has been provided by the investigation of special reactions of lupinine and lupininic acid and by syntheses of norlupinane and j3-lupinane. 

The exhaustive methylation of sparteine was reinvestigated by Karrer,. Shibata, Wettstein and Jacubowitz. At each stage they reduced the unsaturated product formed and so ended up with a pentadecane, C15H32 (b.p. 242°/729 mm., D] 0-7740, 1-43351). The object of this work... 

Karrer and Schmid have examined the water-soluble constituents in poppy straw after extraction of the alkaloids, and have recorded the presence of -hydroxybenzaldehyde, vanillin, -hydroxystyrene, meconin and the following acids fumaric, dZ-lactic, benzoic, -hydroxycinnamic, p-hydroxybenzoic, 2-hydroxycinchoninic, vanillic, phthalic, hemipinic and m-hemipinic, with a more highly unsaturated, carboxylic acid J, b.p. 170-570-02 mm., and three unidentified substances Fa , m.p. 271-2° Wx, m.p. 310° (dec.) and Q, m.p. 260° the two latter are free from nitrogen and contain no methoxyl. 

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