Patent GB-859731-A (GB)
Title: The manufacture of carotenoids
Filed: 1959-02-06
Abstract: The invention comprises 1 : 18-di [21 : 61 : 61-trimethyl-41-lower alkanoyloxy-cyclohexen-(21)-ylidene-(11)]-3 : 7 : 12 : 16-tetramethyl-octadeca hexaen- (2 : 4 : 6 : 12 : 14 : 16)- diyne -(8 : 10)s, such as the bis- 41- acetoxy compound, and a process for the preparation of canthaxanthin or rhodoxanthin by reacting 1 : 18-di [21 : 61 : 61-trimethyl-cyclohexen -(21)-ylidene -(11)] -3 : 7 : 12 : 16- tetramethyloctadecahexaen- (2 : 4 : 6 : 12 : 14 : 16)-yn -(9)- diol (8 : 11) or 1 : 18-di [21 : 61 : 61-trimethyl-cyclohexadien-(11 31)-yl-(11)] 3 : 7 : 12 : 16-tetramethyl-octadecahexaen-(1 : 3 : 5 : 13 : 15 : 17)-diyn- (8 : 10)- diol-(7 : 12) with a lower alkanoic acid, e.g. acetic hydrolysing the reaction product and oxidising with an aluminium alkoxide and a ketone, e.g. aluminium isopropoxide and acetone, the triple bonds being hydrogenated to double bonds by selective hydrogenation, for e.g. with a lead inhibited palladium catalyst after the acylation, hydrolysis or oxidation step.  Suitably canthaxanthine is prepared by acylating 1 : 18-di [21 : 61 : 61-trimethyl-cyclohexen -(21)-ylidene -(11)] -3 : 7 : 12 : 16 tertramethyl-octadecahexaen- (2 : 4 : 6 : 12 : 14 : 16)-yn-(9) -diol-(8 : 11) to give as a result of allyl rearrangement 1 : 18-di- [21 : 61 : 61trimethyl-31-alkanoyloxy-cyclohexen - (11) -yl (11)] -3 : 7 : 12 : 16-tetramethyl - octadecaoctaen-(1 : 3 : 5 : 7 : 11 : 13 : 15 : 17)-yne-(9), which is hydrolysed to the corresponding bis-31-hydroxy derivative, oxidised with an aluminium alkoxide and a ketone to the bis 31-ketone (9 : 10-dehydrocanthaxanthin) and hydrogenated selectively to canthaxanthin.  Alternatively the hydrogenation step may be carried out after the acylation or hydrolysis steps to give a 1 : 18-di [21 : 61 : 61-trimethyl-31-alkanoyloxy-cyclohexen -(1)1 - yl (11)]-3 : 7 : 12 : 16-tetramethyl - octadecanonaene (1 : 3 : 5 : 7 : 9 : 11 : 13 : 15 : 17) and/or the corresponding bis 31-hydroxy compound as intermediates.  Similarly rhodoxanthin is prepared by acylating 1 : 18- di[21 : 61 : 61-trimethylcyclohexadien- (11 : 31) -yl-(11)]- 3 : 7 : 12 : 16-tetramethyl-octadecahexaen- 1 : 3 : 5 : 13 : 15 : 17-diyn- (8 : 10)-diol-(7 : 12) to give 1 : 18-di [21 : 61 : 61-trimethyl-41-alkanoyloxy - cyclohexen (21)- ylidene -(11)]- 3 : 7 : 12 : 16-tetramethyloctadecahexaen- (2 : 4 : 6 : 12 : 14 : 16) diyne-(8 : 10), which is hydrolysed to the bis-41-hydroxy compound oxidised to the bis-41-ketone (8 : 9 : 10 : 11)-bisdehydro-rhodoxanthin and selectively hydrogenated to rhodoxanthin.  If the hydrogenation step is carried out after the acylation or hydrolysis, corresponding bis-41-acyloxy or bis-41 hydroxyoctadecaoctaene-(2 : 4 : 6 : 8 : 10 : 12 : 14 : 16) compounds are obtained.  1 : 18 : Di [21 : 61 : 61- trimethyl-cyclohexadien-(11 : 31)-yl-(11)]- 3 : 7 : 12 : 16-tetramethyl-octa-decahexaen-(1 : 3 : 5 : 13 : 15 : 17)-diyne-(8 : 10)-diol-(7 : 12) used as a starting material is made by converting 8- [21 : 61 : 61-trimethyl-cyclohexen-(1)-yl-(1)]-6-methyl-octatriene-(3 : 5 : 7)-one-(2) by bromination and dehydrobromination to 8-[21 : 61 : 61-trimethylcyclohexadien-(11 : 31) - yl - (11)]-6-methyl-octatriene-(3 : 5 : 7)-one-(2) and reacting with diacetylene di (magnesium bromide).