266 CAROTENOID CARBOXYLIC ACIDS XIII 



3:y:i2:i6-Tetramethyloctane-i:i8-dial C22H42O2 (II): 



The dialdehyde is obtained from a : a'-dihydrox5rperhydronorbixin dimethyl 

 ester by the action of methyl magnesium iodide, followed by oxidation with 

 lead tetraacetate*^. 



CH3 CH3 CH3 CH3 



OHC- CHjCHCHaCHaCHjjCHCHjCHaCHaCHjCHCHjCHaCHaCHCHi,- CHO 



(11) 



The compound is a yellow oil with an intensive odour, reminiscent of ozone. 

 B.p. 18570.3 mm. 



2:6:11 :i5-Tetramethylhexadecane-i:i6-dicarboxylic acid C22H42O4 (III) : 



I I I I 



HOOC-CHaCHCHaCHaCHjCHCHjCHaCHaCHaCHCHaCHjCHjCHCHaCOOH 



(III) 



This dicarboxylic acid is obtained by the oxidation of 3 : 7 : 12 : i6-tetra- 

 methyloctadecane-i : i8-dial with chromic oxide in acetic acid*^. B.p. 220°/ 

 o.i.mm. 



The diamide, C22H44O2N2 is prepared by converting the acid (III) by means 

 of thionyl chloride into the acid chloride and treating the latter with concentrated 

 aqueous ammonia*®. It separates from ethyl acetate in crystals, m.p. 127°. 



i:i6-Dihydroxy-2:6:ii:i5-tetramethylhexadecane-i:i6-dicarboxylic acid dimethyl 

 ester C^^B-.^O^ (IV) : 



This ester was obtained by Raudnitz and Peschel^o from 2:6:11:15- 

 tetramethylhexadecane-i : i6-dicarboxylic acid by the action of bromine and 

 red phosphorus, followed by potassium hydroxide and diazomethajie. 



CIi» CHo CHo CHo 



I I I I " 



H3COOCCH(OH)CHCH2CH2CH2CHCH2CH2CH2CH2CHCH2CH2CH2CHCH(OH)COOCH3 



(IV) 



The ester (IV) is a colourless oil which can be distilled in high vacuum. 

 Concerning its conversion into perhydrocrocetin, see p. 280. 



4:8:1 3:iy-Tetram,i thyleicosane-i :20-diol ( i:20-dihydroxybixane) C24H5QO2: 

 CHo OHo GHo CHo 



I I I I 



HO" GH2CH2CH2CHCH2CH2CH2CHCH2CH2CH2CH2CHCH2CH2CH2CHCH2CH2CH2' OH 

 I : ao-dihydroxybixane 



This diol was prepared by Kuhn and Ehmann^^ by heating perhydro- 

 methylbixin with sodium and amyl alcohol. It is a pale yellow oil which partly 

 References p. 290-294. 



