Conversions of beta-carotene and some related polyenes to keto and hydroxy derivatives by means of N-bromosuccinimide and boron trifluorides
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The reaction of N-bromosuccinimide (NBS) with [beta]-carotene in alcohol-containing chloroform results mainly in the formation of 4-keto-[beta]-carotene, 4,4'-diketo-[beta]-car...
| Summary: | NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
The reaction of N-bromosuccinimide (NBS) with [beta]-carotene in alcohol-containing chloroform results mainly in the formation of 4-keto-[beta]-carotene, 4,4'-diketo-[beta]-carotene, and 4-keto-3',4'-dehydro-[beta]-carotene, Their structures were clarified by relating them to known carotenoids through partial synthetic or degradative schemes. In the course of this work, the following new carotenoids were also prepared: 4-keto-4'-hydroxy-[beta]-carotene, 4,4'-dihydroxy-[beta]-carotene, 4-hydroxy-3',4'-dehydro-[beta]-carotene and 4-keto-[alpha]-carotene.
A reaction mechanism for the conversion of carotenes to ketones is proposed, based on pertinent experiments. The infrared and visible spectra of the new compounds are discussed, and the provitamin A2 effect of the 3,4-dehydro compounds has been demonstrated. Synthetic 4,4'-diketo-[beta]-carotene has been identified with canthaxanthin occurring in some fungi and algae.
The investigation of the products from the hydrolysis and ethanolysis of BF3-carotenoid complexes has been continued and extended: [beta]-carotene, [retro]-dehydrocarotene and 3,4-dehydro-[beta]-carotene have yielded 4-hydroxy-[beta]-carotene. From 3,4-dehydro-[alpha]-carotene 4-hydroxy-[alpha]-carotene was obtained. [retro]-Bisdehydrocarotene gave a new type of carotenoid, viz. 2-hydroxy-3,4-dehydro-[beta]-carotene.
From anhydrovitamin A1 a new isomer of vitamin A1, viz. 4-hydroxy-axeropthene, was obtained.
A photometric method for determining the partition coefficients of carotenoids was devised and tested on thirty-two compounds.
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