【作者】 余衍文；

【导师】 郑大贵；

【作者基本信息】 南昌大学 ， 有机化学， 2008， 硕士

【摘要】 本文选择C6～C12的直链饱和脂肪醛、环己酮、苯甲醛和肉桂醛为代表,利用它们分子中的羰基与VC或异VC分子中的C5、C6邻二羟基发生缩醛化或缩酮化反应,合成了19个VC缩醛（酮）和异VC缩醛（酮）,期望开发具有作为油溶性的多功能食品添加剂、化妆品和药物添加剂。用EI-MS、FTIR、¹H NMR等光谱手段对目标化合物进行了表征。以月桂醛异VC缩醛、环己酮VC缩酮、环己酮异VC缩酮、苯甲醛异VC缩醛、肉桂醛VC缩醛为例,用正交试验优化了合成反应的条件。在优化的合成条件下,苯甲醛VC缩醛的收率24.6%,苯甲醛异VC缩醛的收率38.8%,其它VC缩醛（酮）或异VC缩醛（酮）的收率在67.0～85.8%之间。在溶解度试验的基础上,提出了目标化合物的分离纯化方法。以苯甲醛VC缩醛、苯甲醛异VC缩醛、肉桂醛VC缩醛为例,根据反应机理和构象稳定性原理,对反应产生的顺反异构体比例的大小进行了解释。以辛醛VC缩醛、辛醛异VC缩醛、月桂醛VC缩醛、月桂醛异VC缩醛、环己酮VC缩酮和环己酮异VC缩酮为研究对象,用过氧化值法（碘量法）考察了它们的抗氧化性能,并与VC、异VC以及常用的油溶性抗氧化剂TBHQ、PG的抗氧化性进行了比较。抗氧化试验的POV数据表明,VC、异VC的缩醛（酮）衍生物在茶籽油中表现出明显的抗氧化性,而且随着碳链的增长而提高。异VC缩醛（酮）的抗氧化性优于VC缩醛（酮）。以环己酮VC缩酮、环己酮异VC缩酮和肉桂醛VC缩醛为研究对象,考察了它们清除羟基自由基、超氧阴离子自由基和DPPH自由基的能力,并与VC、异VC以及TBHQ清除相应自由基的能力进行了比较。结果表明,（1）VC或异VC经环己酮缩酮化后,清除自由基的活性未受影响,而且在脂溶性介质中,由于溶解性得到改善,还能更好地发挥作用;（2）当受试物的摩尔浓度相等时,环己酮VC缩酮和环己酮异VC缩酮清除HO^·,O₂^-·和DPPH^·的能力,整体上与常用的油溶性抗氧化剂TBHQ相当。因而环己酮VC缩酮和环己酮异VC缩酮具有作为油溶性抗氧化剂的潜在应用价值。（3）肉桂醛VC缩醛对羟基自由基、超氧阴离子自由基和DPPH自由基均有较好的清除能力。当受试物的摩尔浓度相同时,肉桂醛VC缩醛清除上述三种自由基的能力与VC基本相当,略比油溶性抗氧化剂TBHQ强。更多还原

【Abstract】 With n-alkyl aldehyde（n-alkyl = n-hexyl,n-heptyl,n-octyl,n-nonyl,n-decyl, n-undecyl,n-dodecyl）,cyclohexanone,benzaldehyde and cinnamic aldehyde as examples,nineteen acetal or ketal derivatives of L-ascorbic acid and D-isoascorbic acid were synthesized by the reaction of the carbonyl group in aldehydes or ketons and the C5,C6 ortho-dihydroxyl groups in L-ascorbic acid or in D-isoascorbic acid. These derivatives would possess some similar properties as those of L-ascorbic acid or D-isoascorbic acid,and have the potential applications in oil-based food,cosmetics and pharmaceutical industry as antioxidants,surfactants or emulsifying agents.All nineteen target compounds were characterized by ¹H NMR,FTIR and EI-MS.With n-dodecyl aldehyde D-isoascorbic acid acetal,cyclohexanone L-ascorbic acid ketal,cyclohexanone D-isoascorbic acid ketal,benzaldehyde D-isoascorbic acid acetal,cinnamic aldehyde L-ascorbic acid acetal as examples,the optimal reaction conditions were determined by orthogonal experiments.The yield of benzaldehyde L-ascorbic acid acetal and benzaldehyde D-isoascorbic acid acetal was 24.6%and 38.8%,respectively,and the yield of other L-ascorbic or D-isoascorbic acid acetals and ketals was between 67.0%and 85.8%under the optimal conditions.Based on the solubility test,the procedures for the separation and purification of the target compounds were established.With benzaldehyde L-ascorbic acid acetal and benzaldehyde D-isoascorbic acid acetal,cinnamic aldehyde L-ascorbic acid acetal as examples,the molar ratio of two diastereomers obtained from the synthetic reaction was explained based on the reaction mechanism and conformational stability principle.The antioxidant activity of n-octyl aldehyde L-ascorbic acid acetal,n-octyl aldehyde D-isoascorbic acid acetal,n-dodecyl aldehyde L-ascorbic acid acetal, n-dodecyl aldehyde D-isoascorbic acid acetal,cyclohexanone L-ascorbic acid ketal and cyclohexanone D-isoascorbic acid ketal on fresh tea seed oil was evaluated by peroxide value（POV） determination,and compared with that of L-ascorbic acid, D-isoascorbic acid as well as commonly used lipophilic antioxidants TBHQ,PG.The POV data showed that these acetal and ketal derivatives had definite antioxidant effects on tea seed oil.And the longer the carbon chain was,the better the antioxidation activity of the acetal or ketal became.The antioxidation activity of D-isoascorbic acid acetal and D-isoascorbic acid ketal was respectively stronger than that of its corresponding L-ascorbic acid acetal and L-ascorbic acid ketal.With cinnamic aldehyde L-ascorbic acid acetal,cyclohexanone L-ascorbic acid ketal and cyclohexanone D-isoascorbic acid ketal as examples,their scavenging activity on hydroxyl free radical,superoxide anion free radical and DPPH free radical was tested and compared with that of L-ascorbic acid,D-isoascorbic acid and TBHQ. The results were as follows:（1） The scavenging activity of L-ascorbic acid and D-isoascorbic acid on HO’, O₂^-’ and DPPH’ wasn’t affected by ketonization,but improved in oil-soluble media.（2） When the molar concentration of the tested samples was the same,the scavenging activity of cyclohexanone L-ascorbic acid ketal and cyclohexanone D-isoascorbic acid ketal on hydroxyl free radical,superoxide anion free radical and DPPH free radical was almost the same as that of commonly used lipophilic antioxidant TBHQ on the whole.So both cyclohexanone L-ascorbic acid ketal and cyclohexanone D-isoascorbic acid ketal could have the potential application value as lipophilic antioxidants.（3） Cinnamic aldehyde L-ascorbic acid acetal had good scavenging activity on hydroxyl free radical,superoxide anion free radical and DPPH free radical.When the molar concentration of the tested samples was the same,its scavenging activity on all the above mentioned free radicals was basically the same as that of L-ascorbic acid, and little stronger than that of lipophilic antioxidant TBHQ.更多还原