Phytyl bromide

The first synthesis of vitamin IQ was reported by several workers ia the late 1930s and the synthetic approaches have been reviewed (22). Vitamin IQ was prepared by the reaction of menadione with phytyl bromide ia the preseace of 2iac (23). 

This reaction was applied to the synthesis of quinonoid natural products [34]. Propargyl bromides 62 a and 62b, which were prepared from prenyl bromide and phytyl bromide by a standard procedure, were converted to the corresponding aluminum reagents by reaction with powdered aluminum and a catalytic amount of mercuric chloride [35]. Then the iodomagnesium salt of cyclopropanol hemiacetal was treated with these reagents [36] affording the prenyl derivative 63 a and the phytyl derivative 63 b in 49 and 50% yield, respectively (Scheme 26). 

Compounds of type LXXIII cannot be made by the rearrangement of the 7-substituted allyl ethers, because these compounds yield LXXIV by inversion. a,7-Dimethylallyl bromide,16 7,7-dimethylallyl bromide,29 cinnamyl chloride,84 and phytyl bromide 86 (a vitamin K synthesis) have been used in C-alkylation procedures. The silver salt of 2-hydroxy-l,4-naphthoquinone is converted to a mixture of C-alkylation product and two isomeric ethers by treatment with allylic halides and benzyl halides. ... 

Vitamin has been synthesized from the condensation of the monosodium salt of menadiol with phytyl bromide (24). 

Vitamin E, a-tocopherol, an effective antioxidant, is obtained as a diastereoisomeric mixture in the 2,3 (S),7 (R),11 (R), form and the natural 2,3 (R),7 (R), 11 (R), form (83) by the reaction of phytyl bromide with trimethylhydroquinone in the presence of zinc chloride (ref.86), the phytol required being obtained from chlorophyll. 

Professor Karror, who is fortunately with us and whoso outstanding role will bo properly emphasized by the first speaker at this Symposium, was the first to synthesize a-tocophcrol by eondensing phytyl bromide with trimethyl hydroquinone. He worked out the means of estimating the toeopherols based on the fact that the free compounds readily reduce gold chloride, whereas the acetates do not. His later work included a magnificent study of the relationships of the vitamin activity wnth variations in the molecular structure (Karrer et al., 1938). 

Three types of tocopherol are produced for sale (i) natural tocopherols isolated from soybean, sunflower or other vegetable oils which are mixtures of the a, p, Y and 5 compounds, (ii) natural mixtures which have been methylated to convert the P, y and 8 compounds to a tocopherol (the trimethyl compound) with higher vitamin E activity, and (iii) synthetic a-tocopherol made from trimethylhydroquinone and phytyl bromide. This is entirely the trimethyl compound but a mixture of eight stereoisomers. All three show antioxidant and vitamin E activity but only the last two can be sold as vitamin E. 

Three independent syntheses of vitamin Ki were reported simultaneously by three different groups of workers in the September, 1939, issue of the Joumal of the American Chemical Society. The synthesis of Almquist and Klose (1939) started from phytyl bromide and menadione, that of Mac... 

A new, efficient synthesis of ubiquinone (249) has been described.115 In the key step, 6-bromo-2,3-dimethoxy-5-methylhydroquinone diacetate (257) is treated with l,l-dimethyl-7r-allyl-, 7r-geranyl-, 7r-solanesyl-, ir-decaprenyl-, or 7r-phytyl-nickel bromide (258)—(262) in HMPA at 60 °C, to afford a 70% yield of 2,3-dimethoxy-5-methyl-6-prenylhydroquinone diacetate (263). Ubiquinones-1, -2, -9, and -10 (250)—(253) and 6, 10, 14 -hexahydroubiquinone-4 (254) have been prepared by this method. The preparation of tritium-labelled 5-demethoxy-ubiquinone-9 (255) has been described.116... 

An easy synthesis of prenyl naphthoquinones, e.g. menaquinone-2 (205 n = 2), was achieved by coupling the appropriate prenyl halide with an organo-copper derivative of the electrochemically derived quinone bisacetal (216). Menaquinone-2 and phylloquinone (204) were also obtained in good yields by reaction of 2-methyl-1,4-naphthoquinone (205 n =0) with geranyl and phytyl halides in the presence of metal dust. A one-step method for the preparation of vitamin K analogues uses cyclodextrin inclusion catalysts.Thus reaction of the diol (217) with allyl bromide in the presence of oxygen and/3-cyclodextrin at pH 9 afforded the menaquinone analogue (218). 

In the second approach (B), because of a low initial yield in the first method, the acid-catalysed reaction of the phenol in dioxane containing boron trifluoride etherate with the prenyl alcohol was used. In this way 2-geranyl, 2-farnesyl, 2-phytyl and 2-nonaprenylphenol were obtained in unstated yields, accompanied by the 4-isomer in each case. In the third strategy (C) the prenyl bromide was... 

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