this process comprises reacting phytenal . i . e . the compound of the formula ## str1 ## with a compound of the formula ## str2 ## wherein or is a hydrolyzable ether group , using a chiral catalyst of the formula ## str3 ## if desired , converting a thus - obtained compound of the formula ## str4 ## the residue -- or signifies in the scope of the present invention a group which is cleavable by hydrolysis to form oh . r can be any conventional ether protecting group which upon hydrolysis is cleared to regenerate the hydroxy group which x protects . r is preferably silyl or alkoxymethyl , for example methoxymethyl , or also tetrahydropyranyl . furthermore , the notation &# 34 ; &# 34 ; signifies that the corresponding residue is situated above the plane of the molecule , while the notation &# 34 ; &# 34 ; signifies that the corresponding residue is situated below the plane of the molecule . the reaction of phytenal with a compound of general formula ii is conveniently effected by firstly preparing a compound of formula ii in solution in accordance with the following reaction sequence : ## str5 ## in a manner known per se ( see e . g . l . i . smith et al ., j . amer . chem . soc . 59 , 673 ( 1937 ), r . barner et al ., helv . 62 , 2384 ( 1979 ), r . a . grey , j . org . chem . 49 , 2288 ( 1984 ), houben - weyl , methoden der organischen chemie , 2nd ed . ( 1924 ), vol . 4 , 754 et seq .). thereupon , the compound iii or iv is added . in carrying out this reaction the compound of formula iii or compound of formula iv can be used in catalytic quantities . however , larger quantities of the compound of either formula iii or formula iv can be used . generally it is preferred to utilize about 2 mole % of the compound of formula iii or iv based upon the moles of the compound of formula ii in the reaction medium . in carrying out the reaction to produce the compound of formula v any convenient mole ratio at the compounds of formula i and ii can be utilized with the preferred mole ratio being about 1 to 1 . in carrying out this reaction temperature and pressure are not critical and room temperature and atmospheric pressure can be utilized . if desired elevated or reduced temperatures may be utilized . the compound of formula i is suitably added to the reaction medium containing the compound of formula ii and the chiral catalyst of formula iii or iv . any conventional inert organic solvent can be used as the reaction medium . among the preferred inert organic solvents are those conventionally used in the metalorganic reactions . examples of such solvents are ethers , especially cyclic ethers such as tetrahydrofuran or dioxan , or mixtures of these ethers with aliphatic or aromatic hydrocarbons such as , especially , pentane , hexane , benzene , toluene and the like . the catalyst iii or iv can be used as such or in polymer - bound form . the compounds of formula v are novel and are likewise an object of the present invention . the conversion of such a compound into d - α - tocopherol by hydrogenation of the double bond and cleavage of the protecting group can be effected in a manner known per se ; the hydrogenation e . g . catalytically with hydrogen or by means of alkali metal / c 2 h 5 oh and the removal of the protecting group by acidic hydrolysis or solvolysis . the catalytic hydrogenation is conveniently effected in the presence of a mineral acid ( simultaneous cleavage of the protecting group ). the especially suitable catalyst is pt or pd . the reduction by means of an alkali metal , especially by means of sodium , in ethanol is conveniently effected at an elevated temperature , especially at the reflux temperature ; see also methods in enzymology , vol . xviii , vitamins and coenzymes , part c , d . b . mccormick and l . d . wright , academic press n . y ., 1971 , page 272 . the following example illustrates the invention , but does not represent any limitation thereof . 1 . 6 g ( 5 mmol ) of bromotrimethyldimethoxybenzene was converted into the grignard reagent in a known manner with magnesium in dry tetrahydrofuran and the zinc derivative is obtained by adding 240 mg ( 2 . 5 mmol ) of zinc chloride , which requires 30 minutes . toluene was added and 15 mg ( 0 . 09 mmol ) of endo - aminoborneol are added at room temperature . subsequently , 1 . 2 g ( 4 . 1 mmol ) of ( 7r , 11r )- e - 3 , 7 , 11 , 15 - tetramethyl - hexadec - 2 - en - 1 - al were added and , after stirring for 16 hours , the mixture was hydrolyzed with aqueous ammonium chloride solution . the mixture was extracted with ethyl acetate and the extracts were dried and concentrated . the resulting dehydrotocopherol methoxymethyl ether was hydrogenated in meoh / 1 % hcl over pdc ( 5 %) ( simultaneous removal of the protecting group ). it was concentrated and subsequently chromatographed on silica gel with toluene . there is obtained 0 . 37 g ( 55 % yield ) of d - α - tocopherol . the optical purity was determined by gas - chromatographical analysis of the methyl ether .