Coenzyme Q

Three and one-half grams of 2,3-dimethoxy-5-methylhydroquinone , 14 g of farnesyl - farnesylgeranylgeraniol, and 2.5 g of anhydrous zinc chloride are reacted as described under ubiquinone-9 (VCQ0002). The crude quinone (12.3 g) [ultraviolet maximum at 270 nm ( Three and one-half grams of 2,3-dimethoxy-5-methylhydroquinone , 14 g of farnesyl - farnesylgeranylgeraniol, and 2.5 g of anhydrous zinc chloride are reacted as described under ubiquinone-9 (VCQ0002). The crude quinone (12.3 g) [ultraviolet maximum at 270 nm (Ed^1%_1cm = 52)] is chromatographed on aluminum oxide to give several fractions possessing EEd^1%_1cm =100-142 (2.8 g). Further purification by recrystallization from alcohol or by rechromatography on polyethylene powder yields pure ubiquinone-10(VCQ0001), m.p. 49. Ultraviolet absorption maximum at 270 nm (Ed^1%_1cm =173) (in petroleum ether, b.p.80- 105). Conditions for paper chromatography are the same as described under ubiquinone-9(VCQ0002). (Ref. 0002)

A mixture of 3.4 g of 2,3-dimethoxy-5-methylhydroquinone, 13 g of solanesol, 2 g of anhydrous zinc chloride, 0.2 ml of glacial acetic acid, and 150 ml of absolute ether is shaken under nitrogen at room temperature until a clear solution is obtained. The ether is then evaporated in vacuo at 50; the residue (17 g) is heated at 50 for 15 minutes and then dissolved in 350 ml of petroleum ether (b.p. 40 -45) and 100 ml of methanol-water (7.5:2.5). The petroleum ether layer is washed with four 100-ml portions of methanol-water (7.5:2.5), dried over anhydrous sodium sulfate, and evaporated in vacuo. The residue (13.8 g) is dissolved in 150 ml of ether and shaken with 20 g of silver oxide for 1 hour. After filtration and evaporation, 12.4 g of crude product is obtained showing an ultraviolet absorption maximum at 270 nm (E^1%_1cm =50).
Purification is achieved by chromatography on 350 g of aluminum oxide (activity grade I, deactivated with 7% water). With petroleum ether and 2% ether in petroleum ether, fractions are eluted [ultraviolet maximum at 270 nm (E^1%_1cm =55-114)] , which after evaporation give 3.2 g. This material is further purified by recrystallization from alcohol or preferably by rechromatography on polyethylene powder (Hostalen W). With acetone-water (8:2) pure is obtained, m.p. 45. Ultraviolet absorption maximum at 270 nm (E^1%_1cm =) (in petroleum ether, b.p. 80-105). (Ref. 0002)

From 12.5 g of 2,3-dimethoxy-5-methyl-hydroquinone , 7.6 g of all-trans-farnesylfarnesyllinalool and 5 g of anhydrous zinc chloride 8.3g of crude ubiquinone-8 [lmax 270 nm (Ed^1%_1cm =2113)] can be obtained in analogous manner as ubiquinone-7(VCQ0004). Purification by chromatography on aluminum oxide yields 3.2 g quinone of E^1%_1cm =188. Recrystallization of this material (three times from petroleum ether at - 20 gives 1.77 g of orange crystals, m.p.34-36, which can be further purified by chromatography on 177g of polyethylene powder (Hostalen W). In this way, 604 mg of pure ubiquinone-8 (VCQ0003)is obtained as orange leaflets, m.p. 37-38 Ultraviolet absorption maximum at 270 nm (Ed^1%_1cm =205).(Ref. 0002)

Five and two-tenths grams of all-trans-farnesylgeranyllinalool and 9.3 g of2,3-dimethoxy-5-methyl-hydroquinone are dissolved in 76 ml of absolute ether; 3.8 g of anhydrous zinc chloride is added, and the solution is evaporated in vacuo at room temperature with the exclusion of water. The residual dark brown mass is heated at 45
After filtration and evaporation, 6.1 g of crude ubiquinone-7(VCQ0004) is obtained as light red oil showing an ultraviolet absorption maximum at 270 nm (E^1%_1cm = 125) ( in petroleum ether). The crude ubiquinone-7 is purified by chromatography on the 30-fold amount aluminum oxide (activity grade I, deactivated with 7% water). With 2% ether in petroleum ether colorless and yellow impurities are first eluted, and ubiquinone-7 (2.4 g) is obtained with 5% ether in petroleum ether. The material (E^1%_1cm =208) solidifies on standing in the cold and is recrystallized from a little petroleum ether at -20to give 1 g of orange crystals, m.p. 29-30. For further purification, 0.5 g is chromatographed on 50 g of poly-ethylene powder (Hostalen W). Fifteen-milliliter fractions are collected and stored at 5. Continued to Genetic Information

Six grams of 2,3-dimethoxy-5-methyl-1,4-benzoquinone dissolved in 50 ml of methanol is hydrogenated at room temoperature and atmospheric pressure in the presence of 0.5 g of Lindlar's catalyst until the hydrogen consumptin is terminated (about 30 minutes). The catalyst is removed by filtration, the solution is evapo- rated in vacuo, and the residue is dried under high vacuum for 1 hour. The crystalline hydroquinone is dissolved in 180 ml of absolute ether ; 0.3ml of glacial acetic acid, 3.3 g of anhydrous zinc chloride, and 20 g of all-trans-frarnesylnerolidol are added. The mixtute is shaken overnight at room temperature under nitrogen and then refluxed for 1.5 hours. The solvent is evaporated in vacuo, and the residue is dissolved in 500 ml of petroleum ether (b.p. 30-45) and 250 ml of methanol-water (7 : 3) .
The petroleum ether layer is extracted with three 250-ml portions of metanol-water (7: 3), and the methanolic solutions are reextracted with 250 ml of petroleum ether in a second separatory funnell. The combined petroleum ether sollutions are washed with water, dried over anhydrous sodium sulfate and evaporated in vacuo. The residual brownish-yellow oil (17.5 g) is dissolved in 50 ml of petroleum ether (b.p. 80 -110) and hydrogenatd in the presence of 1 g of Lindlar's catalyst. The catalyst is removes, the solution is evaporated and the residue is chromatographed on 400 g of aluminum oxide (activity grade I, deactivated with 4% water). Eight grams of by-product are eluted first with 3.5 liters of petroleum ether (b.p. 30-45) . With ether (1 liter) 8.3 g of condensation product is obtained which is dissolved in 100 ml ether and shaken in the presence of 20 g of silver oxide for 2 hours at room temperature. Continued to Genetic Information

The compound is prepared in analogy to the procedure given for ubiquinone-3 (VCQ0008) starting from 0.83 g of 2,3-dimethoxy-5-methyl-1,4-benzoquinone and 2.64 g of all-trans-geranyllinalool. Yield 26.4%. Ultraviolet absorption maximum at 271 nm (Ed^1%_1cm =350) (in hexane). (Ref. 0003)

2,3-Dimethoxy-5-methylhydroquinone (0.83 g in 33 ml of absolute ether containing 0.9 g of BF₃ etherate) and 2.0 g of trans-nerolidol are allowed to stand for 18 hours at room temperature and then boiled under reflex for 1.5 hour. The mixture is cooled, the solvent is distilled of in vacuo, the residue is diluted with 90 ml of petroleum ether (b.p. 40-50), and worked up with 70% methanol (3 x 45 ml). The methanol solution is treated with 30 ml of petroleum ether (b.p. 40-50). The petroleum ether solution is washed with water (15 ml) and dried with anhydrous magnesium sulfate. The solvent is removed in vacuo; the product is dissolved in 5 ml of petroleum ether (b.p. 70-100) and chromatographed on 75 g of alumina (activity grade II). Elution with 650 ml of petroleum ether (b.p. 40-50) gives 0.15-0.2 g of a by-product of the condensation; then 220 ml of ether elutes the corresponding hydroquinone as a red oil.
The hydroquinone thus obtained is dissolved in 20 ml of ether and treated for 2 hours at room temperature with 3.7 g of freshly prepared silver oxide. The mixture is filtered, and the solvent is removed in vacuo. The impure product is dissolved in 3 ml of petroleum ether (b.p. 40-50) and chromatographed on 10 g of silicic acid. Ubiquinone-3 is eluted with the same petroleum ether. Yield: 20.3%.
Ultraviolet absorption maximum at 275 nm (E^1%_1cm = 350) (in hexane).
Thin-layer chromatography is carried out on a layer of silica gel impregnated with mineral oil (5% solution of mineral oil in 40-60 petroleum ether). A mixture of dimethylformamide and water is used as a solvent in the ratio 84 : 16. The developer is a 0.25% alcoholic solution of rhodamine Zh-6; the plates are then examined in ultraviolet light. Continued to Genetic Information

To 1.0 g of 2,3-dimethoxy-5-methyl-hydroquinone in 5 ml of anhydrous dioxane is added at 18 - 20 1 ml of BF₃ etherate, and , over the course of 1 hour, 3.35 g of linalool in 10 ml of dioxane. The reaction mixture is stirred for 3 hours and then diluted with ether to a total volume of 150 ml. The ethereal solution is washed (2 x 50 ml) with a 5% solution of sodium bicarbonate and dried over anhydrous magnesium sulfate. The solvent is removed in vacuo, the remaining oil dissolved in 100 ml of anhydrous ether, and treated 18 hours with 5 g of freshly prepared silver oxide and 2 g of anhydrous magnesium sulfate. After filtering and evaporation, the residue is dissolved in 100 ml of petroleum ether (b.p. 40 - 60), washed with water (6 x 100 ml), and dried with anhydrous magnesium sulfate. The solvent is removed in vacuo, and the remaining product is subjected to preparative thin-layer chromatography on a layer of alumina deactivated with % water.
Solvent: hexane-ether (3 : 2). The elution of ubiquinone-2 from the alumina is accomplished with ether. Rf value : 0.56; 2,3-dimethoxy- 5-methyl-1,4-benzoquinone shows Rf 0.36. Yield: 16.8%. Ultraviolet absorption maximum at 272 m (E^1%_1cm = 400) (in hexane).(Ref. 0003) A new regio- and stereocontrolled synthesis of coenzyme Qn (n = 2,3,9,10) is described. Coupling of geranyltrimethyltin with 2,3-dimethoxy-5-methylbenzoquinone was successfully undertaken in the presence of BF₃^.OEt₂. After oxidation of the resulting mixture coenzyme Q₂ was obtained in 90% yield with more than 99% ₁₀ Delta² -trans stereochemistry. Similarly, all-trans coenzyme Q₉ and Q₁₀ were obtained in reasonable yields.(Ref. 0029)

A solution of potassium nitrodisulfonate (6.0 g, 0.022 mole) and sodium phosphate (2.84 g, 0.02 mole) in water (10 is mixed at 25 with a solution of 2,3- dimethoxy-6-methylaniline hydrochloride (2.03 g, 0.01 mole) in water (20 ml) . After 0.5 hour the mixture is acidified with glacial acetic acid (4.0 ml), stirred for an additional 0.5 hour, and extracted with methylene chloride. The dried (MgSO₄) extracts are evaporated in vacuo to an orange oily residue which rapidly crystallizes. The yield of coenzyme Q ₀ is 1.74 g (95%); m.p. 55-57. A small sample is sublimed at 45/1 mm, giving the quinone with m.p. 59. Ultraviolet absorption maximum at 264 nm ( e=13,400) (in methanol). The infrared absorption spectrum shows bands at 1660, 1605, 1450, 1320, 1280, 1220, 1140, 1085, and 885 cm^-1 (in CCl₄). (Ref. 0002)

To a solution of 0.25 g of 2,3-dimethoxy-5-methylbenzohydroquinone and 0.85 g of natural dodecaprenol (possessing eight cis and three trans double bonds counting from the terminal hydroxy-containing isoprenoid unit) in 25 ml of freshly distilled dioxane is added 0.5 ml of freshly distilled BF₃ etherate. After stirring this mixture for 4 hours , it is poured into 300 ml of ether and 200 ml of water. The organic phase is separated, washed with water, and then vigorously shaken with excess aqueous methanolic ferric chloride solution. The ether layer is again separated washed with water, and dried. The residue obtained upon evaporation of the solvent subjected to preparative layer chromatography on silica gel G plates (1.0 mm) developed in hexane-ether (9:1) . Ubiquinone-12 appears as an orange band of higher Rf value than the t of a much larger orange band (2,3-dimethoxy- 5-methyl-1,4-benzoquinone ). Further purification is achieved by preparative thin-layer chromatography using hexane-ether (95:5) as developing solvent. The plates are developed five times, the ubiquinone-12 removed, and this chromatographic process is repeated. In this way, 15 mg of ubiquinone-12 is obtained as an orange viscous oil. The ultraviolet adsorption maximum is at 272 nm (in hexane). Nuclear magnetic resonance spectrum (chemical shifts in t; CCl₄): multiplet at 4.97 (12 vinylic H), singlet at 6.12 (2OCH₃), doublet at 6.92 (J~6.5 Hz) (CH₂ next to ring), multiplet at 7.7-8.2 (side chain methylene), signals at 8.30 (cis methyl at C-3

Methanolic KOH (10%) (2 ml) was added to a solution of 2,3-dimethoxy-5-methyl-6-(3'-methyl-5(5'-methoxycarbonyl-2'-pentenyl)-1,4-benzoquinone (20mg) and pyrogallol (200 mg) in methanol (2 ml) and the mixture was heated at 70 for 1 hr under N₂. Water was added and the reaction mixture was acidified with 10% HCl and extracted with ether. The ether extracts were shaken with a solution of FeCl₃ (1 g) in 30% methanol (10 ml) and the ether layer was separated. The residue of the ether layer was purified by thin-layer chromatography using chloroform-ethanol (9:1) to give (VCQ0013) as an orange oil. Yield 10 mg (52.4 %). (Ref. 0035)

ON(SO₃K)₂(3 g) in water (60 ml) was added to a solution of X (1.4 g) in 2% NaOH (12 ml) and stirred for 2 hr at room temperature. The reaction mixture was acidified with 10% HCl and extracted with ether. The ether extracts were worked up in the usual manner to give an orange oil (1.3 g) . The oil was purified by column chromatography on silicic acid (50 g) containing 3% of water eluting with chloroform to afford <0014> as a red oil: yield 1.36 g (92.3%).(Ref. 0035)

(a) HCl (10%) (0.5 ml) was added to a solution of Q acid-I (VCQ0013) (1 mg) in tetrahydrofuran (0.5 ml) and the mixture heated at 75 C for 1.5 h under N₂. Water was added and the reaction mixture extracted with ether. The ether extracts were worked up in the usual manner to give an oil. The oil was purified by thin-layer chromatography using ether-chloroform-ethanol (3 : 2: 1) to give Q lactone as an orange oil : yield 0.2 mg (20.0%).(Ref. 0035) (b) To a solution of 24.1 g of ceric sulfate in 300 ml of water (acidified with 7.5 ml of concentrated sulfuric acid) is added with stirring within 10 minutes a solution of 7.9 g of crude hydroxy acid (Ref. 0002) in 390 ml of methanol. The reaction mixture is stirred for 15 minutes , then diluted with 850 ml of water and extracted with eight 100-ml portions of ether. The combined ether extracts are washed with three 75-ml portions of saturated sodium chloride solution, dried over magnesium sulfate, and evaporated in vacuo to give 7.1 g (90.5%) of crude quinone . The product is chromatographed on 70 g of aluminum oxide (activity grade II). It is dissolved in 6 ml of chloroform and 20 ml of ether, put on the column , and eluted with ether. In this manner 4.3 g of oily quinone (Q lactone) is obtained which can be distilled at 190-195/0.05 mm.
[Table 0001] (Ref. 0002)

To investigate the protein-ubiquinone interaction in the bovine heart mitochondrial succinate-cytochrome c reductase region of the respiratory chain, a fluorine substituted ubiquinone derivative, 2,3-dimethoxy-6-(9'-fluorodecyl)-1,4-benzoquinone (9FQ) was synthesized. 9FQ was synthesized by radical coupling of Q0 and bis (10-fluoroundecanoyl) peroxide. (Ref. 0016)

The spin labeled Q derivative, 2,3-Dimethoxy-5-methyl-6-[10-(2,2,5,5-tetramethyl-3-pyrrolin-1-oxyl-3-carboxy)decyl ]-1,4-benzoquinone (Q₀C₁₀TMOPOC), was prepared by the esterification of 2,3-Dimethoxy-5-methyl-6-(10-hydroxydecyl )-1,4-benzoquinone and 2,2,5,5-tetramethyl-3-pyrrolin-1-oxyl-3-carboxylic acid (TMPOC).(Ref. 0038)

To a solution of 2,3-dimethoxy-5-methyl-1,4-benzoquonone in acetic acid was added, in portions, the diacyl peroxide with stirring at 90 - 95 C for 1 - 2 hours under nitrogen. The reaction mixture was heated another 10 - 20 hours. The solution was concentrated, in vacuo, to dryness and residue was subjected to silica gel column chromatography. The collected orange fraction was further purified on preparative thin layer plates to give a pure product. (Ref. 0040)

Possible mechanism of conversion of substituted allylbenzoquinones into 6-hydroxychromenes and ""hepene"" homologues is shown in
[Table 0001] (Ref. 0042)

2,3-Dimethoxy-5-methylhydroquinone was condensed with phytol.(Ref. 0007)

Synthesis of 2,3-dimethoxy-5-ethyl-6-decyl-1,4-benzoquinone (5-Ethyl-Q₀C₁₀) --- 5-Ethyl-Q₀C₁₀ was synthesized by a radical coupling reaction between 5-H-Q₀C₁₀ and di-ethanoyl peroxide. Fifty mmol of acylchloride CH₃CH₂COCl, was placed in a 250-ml three-necked flask equipped with a stirrer and a thermometer in an ice bath. One-hundred ml of ether and 2 ml of hydrogen peroxide (65%) were added, and the solution was maintained at 0C and stirred while 4 ml of pyridine was added dropwise over 1h. The ice bath was then removed, and the mixture was stirred at room temperature for an additional 1 h before the ether layer was separated and collected. The ether layer was washed twice with 100 ml of water, twice with 1 N HCl, once with H₂O, twice with 0.5 M NaHCO₃, and once with H₂O, then dried over Na₂SO₄. Approximately 20 mmol of crude di-ethanoyl peroxide was obtained upon removal of solvent.
One-hundred mmol of 2,3-dimethoxy-6-decyl-1,4-benzoquinone (5-H-Q₀C₁₀) (30.8 mg) and 30ml of di-ethanoyl peroxide (CH₃CH₂CO)₂O₂ were dissolved in 3 ml of benzene in a 10-ml round bottom flask equipped with a condenser. This mixture was refluxed for 3.5 h, concentrated under vacuum, and the product was separated directly by thin layer chromatography using a solvent mixture of hexane and ether (3.5 : 1). The Rf value was 0.47. The product band was collected from thin layer chromatography plates and was eluted with ether. The yield was 23.6%. (Ref. 0030)

Synthesis of 2,3-dimethoxy-5-butyl-6-decyl-1,4-benzoquinone (5-Butyl-Q₀C₁₀) --- 5-Ethyl-Q₀C₁₀ was synthesized by a radical coupling reaction between 5-H-Q₀C₁₀ and di-ethanoyl peroxide. Fifty mmol of acylchloride CH₃CH₂CH₂CH₂COCl, was placed in a 250-ml three-necked flask equipped with a stirrer and a thermometer in an ice bath. One-hundred ml of ether and 2 ml of hydrogen peroxide (65%) were added, and the solution was maintained at 0C and stirred while 4 ml of pyridine was added dropwise over 1h. The ice bath was then removed, and the mixture was stirred at room temperature for an additional 1 h before the ether layer was separated and collected. The ether layer was washed twice with 100 ml of water, twice with 1 N HCl, once with H₂O, twice with 0.5 M NaHCO₃, and once with H₂O, then dried over Na₂SO₄. Approximately 20 mmol of crude di-ethanoyl peroxide was obtained upon removal of solvent.
One-hundred mmol of 2,3-dimethoxy-6-decyl-1,4-benzoquinone (5-H-Q₀C₁₀) (30.8 mg) and 30ml of di-butanoyl peroxide ( CH₃CH₂CH₂CH₂CO)₂O₂ were dissolved in 3 ml of benzene in a 10-ml round bottom flask equipped with a condenser. This mixture was refluxed for 3.5 h, concentrated under vacuum, and the product was separated directly by thin layer chromatography using a solvent mixture of hexane and ether (3.5 : 1). The Rf value was 0.52. The product band was collected from thin layer chromatography plates and was eluted with ether. The yield was 33.0%. (Ref. 0030)

2,3-Dimethoxy-5-methyl-1,4-benzoquinone (1.28 g, 10 mmoles) was dissolved in 50 ml glacial acetic acid, and the mixture was heated to 90-95 C under nitrogen. Then, a mixture of diundecanoyl peroxide (7.4 g) in 5 ml of acetic acid was added dropwise over a 2-hour period. The reaction mixture was allowed to stir for another 20 hours at 90 - -95 C , and then evaporated to dryness in in vacuo. The residue was subjected to a silica gel column and eluted with a mixture of heaxne and chloroform. The collected orange fraction was concentrated and further purified on preparative thin layer plates to give 1.4 g of pure product ; yield, 43%. (Ref. 0040)

In a 2.5-ml microautoclave are placed 27 mg (1.17 millimole) of sodium, 0.9 ml of liquid ammonia, and a small crystal of ferric nitrate. This mixture is transformed into sodium amide within 45 minutes at room temperature, as described under isophytol-1,2-¹⁴C₂. (Ref. 0012) Acetylene-1,2-¹⁴C₂ (0.537 millimole) and inactive acetylene (0.49 millimole) are then condensed inthe autoclave, and the mixture is rotated at room temperature for 105 hours. A solution of 650 mg (0.97 millimole) of farnesylfarnesylfarnesyl acetone (purified by chromatography on aluminum oxide and recrystallization from acetone) in 1 ml of absolute ether is then added, and the mixture is allowed to react for 23 hours at room temperature, The reaction product is worked up as usual and chromatorgrphed twice on 20 g of aluminum oxide (activity grade I, deactivated with 6% water, elution with petroleum ether and ether) to give 500 mg of dehydrofarnesyfarnesylgeranyllinalool -1,2-¹⁴C₂. This material is dissolved in 5 ml of petroleum ether and hydrogenated at 6-8 in the presence of 83 mg of Lindlar's catalyst and 1% of quinoline. After 18.5 ml of hydrogen (745 mm, 23) is consumed, the hydrogenation is terminated. The catalyst is removed by filtration, the quinoline is extracted with dilute sulfuric acid,
and the solvent is evaporated in vacuo to give 500 mg of farnesylfarnesylgernyllinalool-1.2-¹⁴C₂. The product is mixed with 750 mg of 2,3-dimethoxy-5-methyolhydroquinone and with 5 ml of a solution of 5 g of zinc chloride in 100 ml of absolute ether, with stirring at room temperature until a clear solution was obtained. The ether is then evaporated in vacuo, and the residue is heated fat 45 for 20 minutes in a rotating flask. the product at taken up with high-boiling petroleum ether, and the unreacted hydroquinone is removed with 75% aqueous methanol. The petroleum ether layer is evaporated in vacuo, the residue is dissolved in 5 ml ether and oxidized with 300 mg of silver oxide. After filtration and evaporation in vacuo, 580 mg of crude ubiquinone-10-1'.2'-¹⁴C₂ is obtained; this is chromatographed on 24 g of aluminum oxide (activity grade I, deactivated with 7% water). With 5% ether in petroleum ether, 260 mg of concentrate is obtained,which is further purified by preparative thin-layer chromatography. The yield of pure ubiquinone-10-1'.2'-¹⁴C₂ is 150 mg. Specific activity : 10 mCi/mg. (Ref. 0002)

To a solution of 2,3-dimethoxy-5-methyl-1,4-benzoquonone in acetic acid was added, in portions, the diacyl peroxide with stirring at 90 - 95 C for 1 - 2 hours under nitrogen. The reaction mixture was heated another 10 - 20 hours. The solution was concentrated, in vacuo, to dryness and residue was subjected to silica gel column chromatography. The collected orange fraction was further purified on preparative thin layer plates to give a pure product. (Ref. 0040)

The total synthetic process, which includes five steps, is shown in Chart 1.
[Table 0001]
Treatment of natural solanesol 1 with phosphorus tribromide followed by reaction of the bromide 2 with ethyl [3-¹⁴C]acetoacetate gave [carbonyl-¹⁴C]solanesyl acetone 3. Wittig-Horner reaction of 3 with triethyl phosphonoacetate gave ethyl [3-¹⁴C]decaprenoate 4. The reaction was employed as it is known to give highly stereoselective formation of alkenes with the E-configuration.13,14 The elongated alkene 4 was reduced with LiAlH₄ to give [3-¹⁴C]decaprenol 5. Condensation of 5 with Co Q₀ hydroquinone borate followed by hydrolysis and oxidation with lead dioxide gave a cis-trans mixture of [3'-¹⁴C]Co Q₁₀ 6.
The crude product was purified by chromatography on silica gel then recrystallised from cooled acetone. The overall radiochemical yield starting from ethyl [3-¹⁴C]acetoacetate was 8.0%. The final product 6 was postulated to contain 1.5% of cis -isomer based on analysis on high performance liquid chromatography of the corresponding deuterium-labelled compound ([2-CD₃3-1'-CD₂]Co Q₁₀) synthesised by the same procedure.(Ref. 0044)

The synthesis of ([2-CD₃3-1'-CD₂]Co Q₁₀) 10 was performed by condensation of deuterated decaprenol 2, and deuterated Co Q₁₀0hydroquinone (2,3-dimethoxy-[5-CD₃]methyl-1,4-hydroquinone 9). The total synthetic process, which includes eight steps, is shown in Chart 1.
[Table 0001]
Basically, the route employed here for the synthesis of deuterium-labelled Co Q₁₀ was the same as that we established previously for synthesising radio-labelled Co Q₁₀.(Ref. 0043)
[1-CD₂]Decaprenol 2 was obtained starting from natural solanesol (all-trans configuration) viaethyl decaprenoate by the same synthetic route as shown previously. The deuteration of decaprenol was performed by treating ethyl decaprenoate 1 with LiAlD₄, and then deuterium oxide. A nuclear component 2,3-dimethoxy-[5-CD₃]methyl-1,4-hydroquinone 9 was synthesised starting from 3,4,5-trimethoxybenzoic acid 3 in six steps. The deuteration ratio and stereospecificity were sufficiently high to enable us to use this deuterium-labelled form of Co Q₁₀in metabolic studies. (Ref. 0044)