Synthesis and Properties Research of Carotenoids and Intermidiates
|Keywords||gadenia yellow pigment crocetin crocetin dimethyl ester antioxidation Wittig reaction Wittig-Horner reaction|
The semi and total synthesis of crocetin dimethyl ester was studied in this thesis, it’s finished by Wittig and Wittig-Horner reaction.First,the crocin was seperated from the gadenia yellow pigment,by gradient elution used methanol/ethyl acetate as eluent. It’s purity was 84.29%,analysed by HPLC.Then, crocetin and crocetin dimethyl ester were obtained by hydrolysis and ester change reaction of gardenia yellow pigment. Purified by recrystallization, their purity were 96.7%and 97.2%.Their data of IR,UV,1HNMRwere accord with references. At last, Using the hydroxyl radical system, superoxide radical system,the antioxidation activities of crocetin and crocetin dimethyl ester were studied and compared with BHT. The result showed that crocetin and crocetin dimethyl ester possessed stronger scavenging activityon hydroxyl radical and superoxide radical than BHT at the concentration of experiment.These results suggested that crocetin and crocetin dimethyl ester would be effective natural free radical scavengers.Last, the ttal synthesis of crocetin dimethyl ester was studied. At first, the intermediate 2,7-dimethyl-2,4,6-octatrienedial was obtained by Wittig-Horner reaction.1,4-dibromo-2-butene reacted with triethyl phospahite,then reacted with 1,1-dimethoxyacetone in base, after hydrolysed in acid, recrystallized by CH2Cl2/ether, octatrienedial was obtained with a yield of 58.7%. Then chloro methyl tiglate was obtained by Wittig reaction. It can be synthesised by 2-bromo methyl propionate reacted with triphenyl phosphine,then reacted with chloroacetaaldehyde, separated by silica gel column, used ether/petroleum ether(1:1) as eluent,the yield was 75.1%. At last, the aimed product crocetin dimethyl ester was obtained by reacted octtrienedial with the ylide of chloro methyl tiglate, the yield was 78.6%. The total synthesis was 7 steps, the total yield was 46.1%(calculated by 1,4-dibromo-2-butene). The qualitative analysis of the key intermediates and the aimed product was confirmed by Mp, IR, MS, ~1HNMR.The preparation of crocetin dimethyl ester from natual and the total synthesis haven’t been researched in our country. The research of total synthesis of crocetin dimethyl ester in this paper can help to develop crocetin and other carotenoids pharmaceutical and the cosmetic used antioxident and antiaging in our country.