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New Enantiospecific Synthesis of (+)-(2R,6R)-(+)-2,6,10-Trimethylundecan-1-ol for Constructing the Side Chain of Natural (2R,4′R,8′R)-(+)-α-Tocopherol (Vitamin E)

“…We reported previously on the chemoenzymatic synthesis of enantiomerically pure chromans ( III ) [2]. In the present study, we developed a new enantiospecific synthesis of (+)-( 2 R ,6 R )-(+)-2,6,10-trimethylundecan-1-ol ( XI ), complementary to chromans III , necessary for constructing the side chain of ( R , R , R )-α -tocopherol.…”

“…Earlier, we developed an efficient method for the synthesis of isophytol V on the basis of ozonolysis of chlorophyll ( IV ) [6]. The dehydration of phytol under the action of p -toluenesulfonic acid and phthalic anhydride [7,8] is known to proceed with a low regioselectivity to give a mixture of 2,4-and 3,5-phytadienes (each as a mixture of E and Z isomers); their subsequent two-stage transformations (ozonolysis and reduction with complex alkali metal hydrides) lead to poorly separable ë 14 -and ë 15 -isoprenoid alcohols.…”

“…The efficiency of the catalysts on silica gel is known for different reactions [9], and Tseokar-10 aluminosilicate was used successfully for condensation of trimethylhydroquinone with isophytol [6] and other vinylcarbinols [10].…”

“…Silica gel L (160-250 µm) of KSKG grade (GOST (State Standard) 3956-76) was used for column chromatography and isophytol V dehydration. Tseokar-10 is a high-modulus Y zeolite-containing aluminosilicate catalyst (produced by Salavatnefteorgsintez) [10].…”

“…A solution of 3 g of TsOH in 20 mL of acetone was added in one portion to 100 g of SiO 2 (160-250 µm); the mixture was stirred vigorously at ambient temperature for 1 h and then evacuated (~2 mmHg, 6 h, 50°ë) [14]. A solution of 1 g (3.35 mmol) of isophytol V (obtained according to [6]) in 120 mL of dry benzene was added with stirring to 16 g of the catalyst obtained (TsOH-SiO 2 ). The mixture was vigorously stirred for 1 h at ambient temperature and filtered.…”