SYNTHESIS AND BIOCHEMISTRY OF ASCORBIC ACID ANALOGUES

抗坏血酸(维生素C)，一种饮食需求 人类健康，是几种酶作用的电子供体， 起到抗氧化剂的作用，并与宿主防御有关 机制、内分泌功能和视觉过程(晶状体)。 最近，人们对抗坏血酸的生物化学重新产生了兴趣 促使人们意识到我们所知的相对较少 关于最佳所需维生素的浓度 这几个角色的运作。在酶制剂的情况下 反应，一个过程的最佳速率定义为该浓度 这使得反应可以达到Vmax，而不会产生毒性。作为以下内容的一部分 一种测定这些浓度的程序，原位动力学 已经对某些与维生素C相关的物质进行了测量 反应。除了检查维生素的功能作用外 C.对高效运输机制的最新表征 维生素C跨细胞膜的转移强调了 维生素对生物过程的重要性。我们有 合成放射性标记6-脱氧-6-碘抗坏血酸作为药物治疗的工具 研究抗坏血酸运输系统的更多细节。 交通研究表明，这将是一个有用的工具，试图 分离出抗坏血酸转运蛋白。为了调查 2-羟基对抗坏血酸活性的重要性 预先制备的2-脱氧-抗坏血酸和2-脱氧-2-卤代 抗坏血酸，包括异构体2-脱氧-2-氟抗坏血酸 以及等极、不可氧化的类似物。环半酮形式 还制备了2，2-二氟-2-脱氧抗坏血酸，其结构 这与脱氢抗坏血酸的环半酮形式相对应 酸。这些类似物的输运性质以及它们的 对降低脱氧抗坏血酸的酶--戊二酸的影响 酸转化为抗坏血酸，目前正在研究中。

Ascorbic acid (vitamin C), a dietary requirement for human health, is an electron donor for several enzymatic actions, functions as an antioxidant, and is implicated in host defense mechanisms, endocrine function and the visual process (lens). Recent renewed interest in the biochemistry of ascorbic acid has been prompted by the realization that relatively little is known concerning the concentrations of the vitamin required for optimum functioning of these several roles. In the case of enzymatic reactions, optimal rate of a process is defined as that concentration that allows the reaction to reach Vmax without toxicity. As part of a program to determine these concentrations, in situ kinetic measurements have been carried out for certain vitamin C-linked reactions. In addition to examination of functional roles of vitamin C, recent characterization of efficient transport mechanisms that translocate vitamin C across cellular membranes has emphasized the importance of the vitamin to biological processes. We have synthesized radiolabelled 6-deoxy-6-iodoascorbic acid as a tool for studying additional details of the ascorbic acid transport system. Transport studies indicate this will be a useful tool in attempts to isolated the ascorbic acid transport protein. To investigate the importance of the 2-hydroxyl group on ascorbic acid activity, we previously prepared 2-deoxy-ascorbic acid, and 2-deoxy-2-halo ascorbic acids, including 2-deoxy-2-fluoroascorbic acid, an isosteric and isopolar, non-oxidizable, analogue. The cyclic hemiketal form of 2,2-difluoro-2-deoxyascorbic acid also was prepared, a structure which corresponds to the cyclic hemiketal form of dehydroascrobic acid. Transport properties of these analogues, as well as their effects on glutarodoxin, the enzyme that reduces deoxyascorbic acid to ascorbic acid, are being investigated.